I have a roommate that is subleasing from me. We have a sublease agreement filled out and signed, and she now has moved out without giving her 30 days, her property is still in my home, and she owes me money. Can I by law hold her things until I receive money?

What state are you in? I don't know how the law differs from landlord-to-tenant to tenant-to-sublet-tenant, but I can tell you that a landlord is not allowed to keep possession of someone's belongings.

How much does she owe you? How much property did she leave behind?