**SPOILERS**
I was surprised so many people hate Roswell, though admittedly I'm a bit biased towards him because he's the one I find most aesthetically appealing. I decided to replay and see what issue was, and there were a few things I noticed:
On the first day he fires off one or two bants that don't really land. It feels like it's supposed to give off a playful teasing nature but no one really fires back or laughs with him so it appears a bit more one sided and mean spirited.
I feel like when he calls Tyson a puppy it should be played off as more banter, but the issue is after this he doesn't do any more bantering. So now whenever he insults Tyson it feels like he's specifically targeting him (which maybe he is, I think that's a reasonable character choice, but it makes him less likeable)
Then there's the conversation with him and Orlando just before choosing a partner. Here a few bants are fired at Roswell and he's got the frowny face on. In fact he's got a frowny face on for most of what should be a light hearted conversation. This kind of gives the impression he can dish it out but can't take it.
After that there's the whole thing with thinking Tyson is incapable of love. So he's prided himself as being a pretty scientifically minded individual. And he gives good reasoning to Dave in the kitchen. And I can see him throwing an offhand remark like "Yea if you're even capable of love." like mild banter. But when they're back in the dining room the way he kind of states it as a proven fact to Tyson's face that he's incapable of love without provocation. I feel like it goes against his character to jump to conclusions and make such hard definite statements. Definitely a bit over the top.
So to sum up: I think the way to make him more likeable is to spread out his snarky comments a bit more among the group, then for the group to retort in kind and for him to take it as good natured ribbing. That way when he makes remarks to Tyson they seem within character and not targeted. But you can still give his Tyson remarks a bit more a sting as compared to the others when the tension rises so it's reasonable when Tyson reacts negatively.
And as a side: I can maybe see after all this how bragging about being the smartest might rub some people the wrong way, and how it might come off as comes off as pretentious. Maybe change it to something like "Well intelligence is an immeasurable quality, so I can't say whether or not I'm the smartest, but I do think I'm the best suited for conducting research and mentally draining tasks." Or just leave him as pretentious, everyone needs flaws. (Or have Dave call him out and that can be part of his arc)