I thought at first this was a genuine mark, but it appears to be a fake mark after further investigation. If this were a genuine older mark, the absence of U.S.A. would not necessarily indicate that it is fake. However, the way the "s" is slanted, according to one of our About.com antiques site users who studies pottery avidly, can be an indication that a Roseville mark is not genuine. Most older pieces will have a slanted "s" in Roseville, while almost all newer marks have an "s" that has little or no slant like the one shown here. Determining fakes solely on the mark used can be tricky. Many times, you have to look at the color, glaze and the way the piece is decorated to determine whether or not a piece of Roseville is authentic. You'll see genuine mark in the next photo, with a fake Roseville wall pocket following.
Note: Check out the Roseville resources link shown at right to view and compare more Roseville marks.