They're smart, independent, tender. They have their own personality, unlike dogs who are always loyal. If they can't get what they want, they can die of depression...
They can love you more than somebody else even if you spend very little time with them. You can't easily buy their love with time and care.
About a partner with pets: it depends.
About a roommate: hey, I wouldn't consider having a roommate at all, let alone roommates with pets.