Well, as with any amp, it's a matter of taste. I know a couple guys around here have roadsters, but I'm not sure about the roadking. Thine Eyes Bleed has at least one for live use, and it sounded pretty damn good when I saw them. Pretty sure John Petrucci used one for a little bit back in the day, but he went back to the Mark IV after that CD.
As for the Mark V, I've played one a while ago and low volume and it was pretty sweet. Clean tones are straight out of the lonestar, and the 3rd channel a has some nice replications of the old IIC+ and MkIV tones, as well as the "extreme" which can get pretty hairy, but they're all very controllable even with near maxed out gain. The basic focused Mark style tone. Really tight articulate, but I found it a tad noisy. Maybe that was just the environment and sub par guitar I was using at the time. The reverb added a LOT of noise to the mix though, which I didn't particularly appreciate, though I don't really like spring reverb.
Channel 2 is what killed the Mark V for me. I was playing it unboosted, so that could have been part of the problem but there's just SOOOOOOO much low end. It's just THICK. I had the bass off and still found it too bassy for a lead tone. I'm sure with more than 20 mins I could have gotten something out of it, but a 3 channel amp with the variety of tones available, and not being able to use one of the channels (the way I wanted) was what ultimately drove me to not buy it.
I'd love to go try another one again with my OD pedal in hand and really try to tweak the shit out of channel 2 to see if i can't get some good lead tones. This little review might be a tad unfair to channel 2, and I'm sure a lot of people love the shit out of it. Just not my "cuppa" I guess. That said, channel 1 and 3 are fucking PHENOMENAL. especially channel 1. I honestly found it hard to dial in a setting I DIDN'T like.
So take that with a grain of salt as always, and go try it out for yourself. I just didn't get along with channel 2 all that well. Other than that, it great.