Pittsburg is not a very big place and any convenience store or gas station you stop at should be able to tell you how to get to Rose Hill Cemetery. I used www.switchboard.com
and found the following that might be helpful to you:
1. Pittsburg-Camp Co. Library, 613 Quitman St., Pittsburg 75686, 903-856-3302
2. Erman Smith Funeral Home, 315 Rusk, Pittsburg 75686, 903-856-2711
3. Johnson Funeral Home, 220 Fred, Pittsburg 75686, 903-856-3762
I know the Pittsburg Library has a book that was written on Rose Hill Cemetery (late 1980's I think) by John P. Frazier. I doubt Mr. Frazier is still living, but I phoned him during this time and he met me and took me to the cemetery. The folks at the Library were most helpful also!
Good Luck on your visit to Pittsburg! And be sure to eat some hotlinks while you are there!