Nope; Dash is an action, and so he couldn't attack (this is the real place where initiative order matters). There's a feat, the poorly-named Charger, that would let him attack in these circumstances.
I'm thinking about buying an extra PHB and keeping a copy in my office. That's embarrassing, both to admit and to do.
Sure, I think that's reasonable. I'm not sure if Strahd knew it was only a bonus action to activate Roscoe's rage, or that the rage ends if he hasn't attacked a hostile creature or taken damage that turn. Seems like he would be his own best advocate in this arena. Then again, several us are still learning the 5e system, so maybe he truly didn't know. One of the things that's been tricky for me is (wrongfully!) assuming I know how something works in 5e because I know precisely how it works in 3.x.Roscoe loses his rage if he doesn't attack or get damaged in a given round. Since the movement and positioning have been difficult to keep track of and conceptualize, can he reclaim that use?