Remember Ruger lists "rosewood" to describe one of several reddish-orange types of wood, not all hardwoods.
As a commercial offering, rosewood as-sold can be Indonesian, Pakistani, East Indian, Madagascar, Nicaraguan, Malaysian, etc. A few second of websearch reveals they are all sub-species of Dalbergia, and are a reddish fragrant soft wood. The primary sub-species was declared endangered worldwide since '92, and trade in that wood is prohibited.
Since then laminates of cheaper "rosewoods" have been used in the USA. Color is not uniform and can range from reddish to almost black to red-purple.
Anyway rosewood is not a single type of wood... I have not experimented with anything other than Tru-Oil. I am not a grip-maker.