Weight gain is pretty much proportionate to how much you eat, even for good weight gain. You won't pack on 20 punds of muscle unless you take in a bunch of calories to do it. So if you do end up munching down a bunch of protein supplements, they can help you get more weight and mass by providing you with the extra calories to gain weight. Personally, I'm not a big fan of supplements. I think that most things can be gotten through diet. If you have any fat to spare, you can lose that while gaining muscle if you keep your diet sensible. That said, if you are down to zero fat, you can expect to pack on a few pounds of muscle here and there.
As far as cutting back on your cycling time, it depends on how hard you lift and what your goals are. I am trying to bulk up, because I am vain from having lost a ton of weight and want to show off what little muscle I have. So when I hit the gym on my legs days, I can barely walk the next day. I can still ride, but it's going to be a recovery ride for sure and not a hammerfest. But for the last year, I did full body workouts and toned up a lot. I could ride whenever and it never got in the way of cardio. Either way, you have to be careful to incorporate rest days so your muscles can recover.
I'm sure other people will have much more incisive things to say, but this is what has been working for me. I am constantly making gains in the weight lifting and speed departments, although to be fair I was in terrible shape when I started. Good luck!