Does your hard drive light go crazy when these freezes happen? Is the momentary freezing worst at the beginning of a match or when you first launch the game after booting up, and does it get better or go away entirely the longer you play on a map? If so, I'd blame your hard drive.
Unfortunately (or fortunately), Red Orchestra's game engine does not pre-load a lot of game data from the hard drive onto RAM during the initial loading screen, which necessitates a lot of streaming in of textures, geometry, objects, terrain, etc, during actual gameplay. On one had, this not only cuts down quite a bit on initial loading time but also uses very little VRAM (I see <500MB usage at High settings). The downside to this is that those momentary freezes are unavoidable if you've got a slow mechanical hard drive as they simply cannot compete with the lightning-quick access time of an SSD.
If this sounds like it describes your problem,
here is some more useful info.
The only way to really get rid of all the in-game momentary hiccups is to get an SSD, but you could possibly improve it by defragmenting your hard drive, optimizing your page file, or
increasing the game's texture pool size (at bottom).
If anything, I feel fortunate that Red Orchestra's data management isn't as bad as some examples out there. Diablo III has absolutely horrendous streaming issues and is basically unplayable IMO if installed on a slower mechanical drive. Source engine games also get a lot of freezing due to the same problem.
I can usually make Red Orchestra 2 completely stutter-free if I spectate for about a minute before joining and just roam around the entire map, letting everything preload to RAM. Obviousy, the best thing would be if the game would just load everything into RAM intially like Battlefield 3 does and never access the hard drive during gameplay, but I think this is more a limitation of Unreal Engine 3 than anything else.
