There doesn't seem to be any rule or pattern in how such words are written. Clearly reuseable and resaleable should be allowed as words, but should they be rare or common? According to a couple of sources, the spelling saleable is used more often than salable, but resaleable is used less often than resalable.
I think the least confusing course will be to go for consistency, so both of the added words will be classed as common.