Do you share anything with your roommate or do you keep your stuff to yourself?
A mini fridge, a mirror, and a fan.
There are “hardware” items like microwaves, printers and refrigerators that are often shared. It is betst for each person to own one item…e.g.you own frig and they own microwave. If you use their printer, then you buy ink or paper next time. For consumables, I think the main thing is that things even out…don’t let the other person keep eating your food with out reciprocation.