There are different densities of Rosewood so the softer ones will mark more easily. Some have found little or no problems with rounds on Rosewood. Coatings can help but that might change the sound of the bass. Some have used superglue to coat the board. Other than that what has been said above.
Flats, rounds and half rounds all have their plusses and minusses. Flats have a duller tone with lots of thump. Rounds the opposite. On a wooden board they have a sharp attack and a very bright clear decay to the tone. I don't think you can beat the tone of rounds with the decay part of the tone. However, I don't like that sharp attack they have. Halfwounds/rounds do it for me. They have about three quarters of the brightness of a round string to begin with but with a much softer attack to the tone. They can be a bit sticky to begin with but after a few days they become very slippery. More than a round. They keep a great tone for much longer than a round would, IME.