Yes, it is indeed distinct. “Roommate” does not imply any sort of landlord/tenant relationship. It’s just someone you allow to live with you. This is the route I would choose, unless they demanded tenant status.

The downside is that if they refuse to pay rent at some point in the future, it’s tough to take them to court over it since you don’t have a formal rental agreement.

sublet (original tenant moves out but can return and it doesnt alter tenant/landlord relationship)

FTFY. There is no requirement that the principal tenant actually leave the premises. “Subletting” is where the owner of a property leases to a principal tenant, and that tenant leases to additional tenants. The owner of the property has no agreements in place with those additional tenants. You are the tenant of the owner; the “college student” is your tenant. You are subletting (part of) your rented space to another.