Thrips is/are an insect: Frankliniella occidentalis -- Western Flower Thrips. Yellow sticky cards are useful as a biological control. Spinosad is said to be effective.

Spider Mites are NOT an insect.
Spider Mites are an arachnid -- like spiders, and ticks. Insecticides don't kill them, and use of broad-spectrum insecticides kills the "good bugs" that prey on them, and makes the problem worse.

Avid is a chemical control ... but the most-effective control for spider mites is hose-washing the plants, FROM THE BOTTOM UP, as the mites are on the UNDERSIDE of leaves.

Jeri

Mites are not quite insects, but close enough. The common Two-Spotted Mite (red spider mite) infests lower leaf surfaces and sucks the plant juices. The upper leaf surface will be finely stippled with a slight grayish-yellow pallor. Later the leaves dry out and curl. The lower leaf surface looks dirty. Noticeable mite damage starts toward the bottom of the plant and moves up. You will need a 4x-6x hand lens to see the mites and their webs. Spider mites are controlled by a hard spray of water directed repeatedly to the lower leaf surfaces. Most of the time, natural enemies keep them in check, but they can explode during hot dry weather. Roses grown inside or under eaves will get worse mites, because rain deters them.

Flower thrips are barely visible insects that feed on flower petals. Infested flowers will look dirty and scratched. Petal tips and edges turn brownish. The thrips are elongated, amber-colored, and less than 1/16" long. They scurry when you separate the flower petals. Often there is an outbreak of thrips toward the end of the first flush of roses. They may then subside because insect predators eat them. The recommended insecticide is spinosad, but I just wait them out. Thrips are all over the yard and neighborhood and they are highly mobile, flying to the flowers.

The main difference in damage symptoms between spider mites and thrips damage is that thrips are usually associated with irregularly shaped white or greyish-white spots distributed mainly along the mid-rib and side veins of plant leaves; while similar symptoms caused by spider mites are distributed randomly on leaves. Found this at http://old.padil.gov.au/pbt/index.php?q=node/13&pbtID=116 In addition, I see the leaf turning bronze colored then looking at the underside of the leaf with a magnifying glass can see small white "dots" moving around. This is the mite.
You will need to use a "miticide" to controll or kill the mites. It is difficult to do and you have to us a regular spray program. Miticides can be expensive, but I found a Spectricide product at my local Ace hardware that works for me.

Just a note on thrips.

The Knock Out family seems to be particularly attractive to thrips. So much so that we can use our Knock Outs as "canaries in the coal mine" to give us an early warning that thrips are around and we should be on the lookout for them on our other roses.