Oops, I forgot to mention - the compost will be homemade & it'll include copious (I really do mean copious!) amounts of horse manure & a lot of coffee grounds. I may also add alfalfa.

I guess I'm wondering - should I include anything to promote bloom?

Thanks for any input!

The best mulch you can use is what ever material you can get at the least cost, so homemade compost would be a very good mulch and any of the others that were free or very low cost would also ne good. If a lot of material to use as mulch is available pretty much for gree there is no good reason, ever, to spend money purchasing it.

Manure is relatively high in salts. Roses are salt sensitive. As salts leach out of the mulch and into the soil by rain and irrigation, the roses could start showing some symptoms of salt toxicity such as burning at the tips and margins of older leaves, poor vigor, and discoloration of foliage. What percent of that concoction is manure and how thick are you gonna slather it on?

I don't know how thickly I'll slather it on! How much will be too much? I had no idea - I've seen veggie gardens where people use several inches of manure as mulch.

Most vegetables have moderate to high tolerance for saline soil conditions. Besides, a little tip burn on your peppers won't matter since what you're after is peppers. (Although high enough salts can decrease yield).
Roses are salt sensitive and much more likely to burn in soils where salts are even slightly elevated. And burnt foliage matters on roses since their "crop" is aesthetics.
Since you'll get the organic matter you need as the wood and leaves decompose and you're supplementing nutrition with fertilizer, I'd say skip the manure.

Huh, good to know that roses are that salt sensitive & manure is high in salts. I've so often read that roses favor manure over other fertilzers. Are all manures approximately equal in salts?

We might (then again, we might not) get a lot of rain this winter (kind of the burning question for California gardeners right now). If we get a lot of rain, I might feel more comfortable with giving them some manure. But, I won't give them nearly as much as I had thought I would!

I've so often read that roses favor manure over other fertilzers.
Yeah, the vast majority of people who write gardening books and gardening columns are first and foremost (gasp!) writers. They also happen to have an interest in horticulture, rather than horticulturalists who take an interest in writing. You'll read all kinds of kooky stuff out there from "experts".
Some manures are higher in salts. Some are lower. they're all too high to be used in "copious" amounts on roses. If you use a small amount and rains this year are sufficient to flush excess salts beyond the active root zone, you'll be okay. I just don't see why you would add something that could be a problem if you are already getting plenty of organic matter and fertility from other sources. But (shrug) whatever floats your boat.

Manures should never be used as a mulch since that simply exposes the nutrients the manure does contain to either escaping to the atmosphere or just leaching through the soil as rain falls and polluting the environment.
Manure should be composted and then applied to the soil, or tilled in very shortly after being applied to the soil, a very poor second choice.

You'll read all kinds of kooky stuff out there from "experts".

Boy, ain't that the truth!! And you'll also find no small measure of "kooky" stuff here on GW :-)

If you include the manure in your compost as an ingredient, a lot of the harmful salts will be broken down by the composting process, as will the potential of the stuff to 'burn', which is the result of high levels of ammoniacal nitrogen (horse pee). Since roses are not an edible crop, there are far less concerns about the need to compost manures before applying as a mulch or topdressing - most of those derive from the potential to spread pathogens to edibles from uncomposted manures. But aging the manure IS a good idea, as this will also allow for the dissipation of the salts and the ammoniacal nitrogen. If you are mulching now for winter, even fresh manures are unlikely to cause much harm, as the plants are dormant, or in your case, resting for the season and by the time the soils rewarm and growth starts again on the roses, any manures will have aged inplace and the potential for 'burning' eliminated.

If one has the choice, I would opt for rabbit manure for roses over and above any other manure type. It doesn't contain high levels of salts or ammoniacal nitrogen and can be used directly on the garden, edible or otherwise, without aging or composting. Plus, it is heavily alfalfa based (barely digested alfalfa) and contain a natural growth hormone, triacontanol, which roses react to with extremely positive results.

Lacking rabbit manure, I would use whatever organic mulching material was readily at hand - nutrient offerings on all are pretty low - but supplement with a springtime application of alfalfa meal as well.

If you include the manure in your compost as an ingredient, a lot of the harmful salts will be broken down by the composting process
Yes and no. In some cases, as in the burn potential of ammonium, some will volatilize and will be lost to the atmosphere. However, some of the ammonium will also convert to nitrate, which has greater osmotic potential and contributes more to the burning of plants than ammonium does and is not volatile. (Fun fact, when ammonium converts to nitrate, oxygen hooks up with the nitrogen atom to form [NO3]. In order to do that, the ammonium [NH4] gives up it's hydrogens, which is a primary factor in the decrease in the pH that you will see as manure decomposes)
Also, composting does precisely nothing to break down or sequester things like sodium and chloride (a couple of the big culprits when it comes to burn secondary to manure application not only due to osmotic potential but also due to specific ion toxicity). They're elements, and if composting could split atoms, homeland security would shut us all down.
Manure can break down all the live long day but unless it is accompanied by leaching to flush salts, either out of the pile as it's composting or after it's applied, significant burn potential remains. If the leaching occurs after it is applied (even if it's been "aged") the salts are going to grow straight to your root zone on their way to the sub soil. Of course, the dose makes the poison.

As far as rabbit manure goes, I'll have to take your word for it. I don't know jack (rabbit) about it.

"I guess I'm wondering - should I include anything to promote bloom?" Banana peels.

Your manure, coffee grounds and alfalfa will provide some N, but you need some P and K for those roses and banana peels will provide some.

I used to do roses but on this property I can't since the deers love them too much. I still add lots of banana peels to my compost for the perennial beds, but when I had roses I used to simply bury the peels around the base of the plants. I never used manures, but did use alfalfa pellets diluted and spread around the base as well as UCGs mixed into the soil a bit before mulching with shredded leaves for the summer. Worked like a charm! Austins were my favourites and to this day I still have two Lillian Austin roses which I refuse to give up. :O)

I can understand why you don't want to give up on your Lillian Austins! I don't have LA, but I have a lot of English roses, and I love the form & fragrance, with the exception of myrrh.

I'm adding banana peels to my compost, so that's part of the mix. I've heard of people burying the peels by the plants - maybe I'll do that with the ones needing special attention.

I may try seeking out rabbit manure. I like that it already includes alfalfa, and if I can get it for free, the alfalfa's free! It should be easier to deal w/ than horse stuff! I've seen mention on various sites that aged compost has less salts. This bears further research....