From what I saw, a lot of early levels use Rollers (exactly because of the reasons you stated), while 10+ almost always use guns. Rollers-only and Gunners-only team were always shitty for me. But when I´m the only roller with 3 gunners to back me up, we are a lot more effective to cover territory.
That´s one more thing I forgot to mention, we absolutely NEED a way see which weapons our team plans to use, and have at least some seconds to change pre-battle. I was testing a charge gun and my team had 3 other people with charge guns, we lost horribly because those things were meant for killing, not painting...