The only time I've had trouble getting groups on my rogue was sitting in mistmoore at prime, when everyone else is sitting waiting in a queue for a group. The biggest thing you can do is to make sure you're not /role or /anon as people looking for good DPS to fill out their groups will do a /who all rogue and seek you out from across the server. Set /lfg on as well... even though you can't filter a /who with LFG, the tag will still show up in any query you'd regularly show up on.
Most XP groups aren't going to be inspecting your gear before inviting you either, and won't even care unless they see you doing silly backstabs, then they start inspecting gear and wondering what that small dragonbone shard is in your primary (if your a stubby race).
Apparently at some point before rogue epics were restricted to being equipped before 46, people that didn't have their epic (at say, level 20?) were getting denied groups.... which is pretty ridiculous
[You must be logged in to view images. Log in or Register.]
The best thing you can do is make a list of good tanks/heals/CC that you've grouped with at lower levels and friend them as this will help you find groups at later levels.