Rickenbacker are the only brand I can think of that bothers with sealing rosewood fret boards and they come up just like a Fender Maple one to touch.

As Simon said part of the reason for having rosewood is the different feel plus a bit more mellow tone. Lacquered maple boards tend to sound brighter.

Andy is on the money with DT Wax as I have used lemon oil which helps to clean and seal the timber whereas the wax also fills the grain plus it lasts longer before needing another application. Best to go with DT Wax first. Bit of effort on a dry board but well worth it once finally done.

Cheers, Waz