I should let actual Roscoe players describe the tone, but in the meantime, head to the Rocket Music area under Sponsored Forums and listen to Greg's recordings to get a good idea. It's a great Roscoe 101 class including different pickups, different preamps, different models, and yet a common Roscoe family of sounds to my ears.
Sound Clips Featuring Greg Bump | TalkBass.com
I hear rich mids, a warm but tight low end, and an articulate top. To me there is a Smith'esque sound that is a little broader in the mids (the Smith being very focused) and less pingy than the Smith which I would describe as a smoother top end.