Can we rent out a room with reverse mortgage?

If the terms of your written mortgage with the lender does not prohibit it, yes. Reverse mortgages are usually only given to elderly homeowners who are making the house their permanent residence and not making it a rental property. Whether your making it a semi-rental property is barred depends solely upon your written contract [the parole evidence rule forbids relying any oral language from changing the terms of the written agreement].