Whose name(s) is/are on the mortgage?
WE are both still on the mortgage.
we have not changed anything about how we own the house since we bought it.
First of all, any rent your roommate pays to you is considered "other income" and should be included on Line 21 of your 1040.
Secondly, you and your ex-husband can legally deduct the portion of the mortgage you paid, so long as both of your names are XXXXX XXXXX mortgage. However, as far as your ex-husband goes, mortgage interest is only deductible on your "main" and "second" homes.