That sucks your roommate can't do over normal lol. Jeez.... Normal is so easy you can basically melee everything and almost never die. Hard is barely challenging. Legendary is fairly easy for most parts, there's only a few spots where it's really hard.

I only play on Legendary and I always beat it on solo. Have added some skulls to it to make it harder, but adding too many is just ridiculous hehe.

You have the Master Chief Collection?