Deer laugh at a 5 ft fence. Eight feet is the recommended minimum, and local nurseries outside of populated areas go for ten.

my first guess.

Yes, best guess is deer but don't rule out those rabbits either. I've seen them standing up on their hind legs munching on mine. Or they chew off up as high as they can get and sever the branch and eat it. If possible add another 3 feet to the top of your fence and then cage the bottoms of the roses against the rabbits. It ain't pretty but it works.

My choice is DEER. The local rose garden in the park had a HUGE deer problem until they had a twelve foot fence installed. Now the garden is lovely all year. If it is a chain link fence the deer can see what there is to eat and will happily leap a five foot fence.

It sounds exactly like what happened in my yard a few years ago. I fenced my front yard in. We pay through the nose in taxes for the previlege of living in one of the heavily regulated jurisdictions in the U.S. so the fence naturally cannot be go higher than 6 feet and cannot be anything less than cast iron or alumium under town ordinance. And of course that it does not work. To show their contempt at my feeble attempt to thwart them, a herd of day left an extraordinary amount of fecal matters on my walkway a few days after the fence was put in. So, in addition to the fence, I have been using a combination of Repellex (which supposeldy makes the roses taste bad to critters) and lots and lots of Milorganic (made from raw sewage, the stink is what supposedly repells deer). So far, so good. But I am knocking on wood as it only takes one deer to destroy my rose reason...