I'm not trying to self promote here, although it might seem like it! I am a member of another games forum (primarily UK users although we do have many other nationalities too).
We often try to get friendly online sessions and competitions going to keep RB alive, but we always fall short of PS3 players and it generally ends up as just the 360 members taking part, leaving the few PS3 players we have on the sidelines.
If anyone would be interested in padding out a PS3 band or two I'll include a link to the forum below and maybe you could get in contact with our PS3 members over PSN (no need to sign up to the forum, unless you really want!)
We plan on getting together Sunday's at around 7pm BST and sticking to a theme each week to get people playing their DLC online (disc songs wear thin quickly don't they!) I imagine bands will maybe stick around afterwards though and play other songs too.
I'll keep an eye on this topic and pass any interested people on to our PS3 members and hopefully we can get something regular going for them.
Also! If the date and times are not good for people, let me know and I'll try and move things around. Usually early evenings are better as it's harder to find a drummer as the night goes on!