I'm Alison and I have four characters here, although you wouldn't think it because I've bren conspicuously absent for the last week or so. All of mine have boring usernames, accio and then their name.
I'll start with my girl because that's probably where Roger would start ;-) She's not blonde but she's pretty and she loves cute boys. She'll happily have briefly dated or kissed Roger at some point - as she went to the ball with Cormac, we have established she is fine with arrogant guys, possibly because there's plenty to argue with them about. She is friends with Amelia, though, so she might not be best pleased with him at the moment. Mel (Demelza Robins) is a fifth year Gryffindor, Quidditch enthusiast, though she's yet to make the team, and Hogwarts resident feminist/Marxist/friend of whatever oppressed group she can find. She loves debating and telling people they're wrong. Roger may also know her dad, who is a sports journalist.
This here is Lee. Lee is pleased to have another boy to talk girls with. He likes girls. He's not the chest-baring type, though. He's just really nice to girls and loves them, and can be a bit of a kiss-slut. He's very gentlemanly and nice about it though. He is, obviously, the Quidditch commentator and he misses it so much it hurts. He will respect Roger for his Quidditch skills. Lee is a terrible flier but knows more about Quidditch than anyone. He's pretty laidback, likes finding rules to break and instigating mischief. He'll be friendly with Roger. He's team Harry, though, and quite obnoxious about it, so if Robert is likely to be put off by that, let me know!
The other boy Roger will know is Barney. Barney is a sixth year Hufflepuff and usually the Hufflepuff keeper. He's incredibly bouncy and outgoing, talks in run on sentences and is not the brightest in the bunch. He's very sweet though and he loves all sports and exercise. He will be friendly because that its his default mode, but I imagine if Samir is too much for Roger, Barney will be too. Still, Quidditch respect.
Finally I have Yakov, my Durmstrang boy. He's a seventh year. He is the laziest person ever. His hobbies are eating and sleeping. He is basically a pushy parent's nightmare and a pushy parent's reward. He's a nice guy and actually quite sensitive underneath it all, but sometimes puts people off with his poor hygiene. I don't imagine Roger will have much time for him.