I received a 1099k from Paypal, but the money I received wasn't for a business, it was from my roommates to pay their portion of the rent. How should I enter that info?

You don't need to do anything with this 1099-K. As a reimbursement for a personal expense, it is not considered income - for tax purposes or anything else.

 Form 1099-K, like all 1099 Forms, is an information return. If it doesn't reflect income, you don't need to account for it on your tax return. If it did reflect income, you would need to account for it elsewhere on your return.

(There isn't even a place to enter Form 1099-K on your tax return).