I watched a lot of Moose (Meese?) games this year out of interest in Kyle Connor. Roslovic looks like a smart two-way type with good hockey sense and decent defensive awareness. Those are his strengths. He is not overly powerful in any way but definitely has useful speed and certainly tenacity. I think you are looking at a Philip Danault, Mathieu Perreault type. Not a huge build, but fast and smart. I think if he turned out like Thomas Plekanec or Frans Nielsen, that's the type of player you should expect. It's what I see anyway. If Scheifele is the long-term #1 C in WPG and Little is the #2, Roslovic is the #3 and he could be the #2 when needed.
As far as timeline, I think he is NHL ready for camp next year and gets a job. He won't be overmatched in the NHL, as long as he's not asked to carry any big loads.