Blueger's a forward who's best at C but can play at W. He plays a 200 foot game - very defensively responsible and smart, but also a good playmaker and shot. Decent foot pace, decent size, very smart. There's almost no flaws in his game. I'd expect him to stay in the NHL for the foreseeable.
Johnson's a forward who's best at W but did play at least some C in the AHL. He's another 200 foot player and his main attributes are his speed, speed and speed. Like, he might be only a shade slower than Hagelin. Decent enough hands and IQ too. Bit on the slight side, but seemed to do okay with that. I think it's probably 66/33 as to him being in the AHL or NHL next year, but I think there's probably an NHL future there.
Riikola is a left hand dman who can play a bit on his off hand. He's a weird fish in that he noticeably does a lot of things very well - skates well, big physicality for a medium sized guy, smooth skills - but it never seemed to add up to big overall impacts. I think he probably has an NHL future but may be wrong, and I'm not sure its with us.