The word sprints and setting aside time are things I was going to say/suggest (good thing I looked at the comments first, huh?), and they can honestly be really helpful. I've only ever written a novel for NaNoWriMo, but those word sprints can be a serious help. You can also find programs that reward/punish you for writing (you set the parameters on things like Write or Die or Written Kitten (I think that's right) and they have web-based ones so you don't have to pay/download). There are also free writing software programs out there with timers (I cannot remember the one I'm thinking of right now, and I'm sorry for that) and/or word goals (whichever you find is easier for you). And also try working on your novel when you know/feel you're most creative. Is it first thing in the morning? Wake up a little earlier. Late at night? Set aside some time before bed where you can write or sign off early from rp when you know you don't have anything pressing the next morning so you can write into the wee hours. And so on.
Another thing I will suggest that helps me (especially when I don't have access to a computer) is carry a notebook or two around (and it doesn't have to be a big/full sized one, either, but the smaller ones that fit in purses and pockets). You may know that already, though, but if you have one that's just for your novel, you can jot things down whenever they hit you, and you can either copy it right onto your computer when you get home or you have scenes/ideas that you just have to flesh out and expand on when you're home. And I say get two because one can be for rp, where you jot down what you want to have happen in a scene or a journal entry so you can breeze through it when home and not take away from that novel writing. And if you have a 9 to 5 type job, write a little bit on breaks and during lunch. Any pocket of time you have can be spent getting a few words down for your novel (unless it's sitting at a red light while you're behind the wheel. That may not be too safe. But any non-risky free time works!) or even a few words down for rp.
And like another commenter said, let your rp partner(s) know what's going on, and if you set aside the same time almost every night, you can even say, "Hey, from this time to this time, I am for sure working on the novel so don't expect replies in any form. I'm not ignoring you to be rude. I just need to focus." Then disconnect from the internet (and maybe turn your phone on silent) unless it's absolutely necessary. If it isn't, do whatever research you think you'll need before, set things to be viewable offline/save internet pages so you can pull them up but not risk the pull of the internet, get out all social networking urges if you have them, and then just write.