I'm having a problem coming up with the CR for a goblin with advanced class levels. Namely: Rog1/Ftr5, Rog2/Ftr6, Rog3/Ftr7, Rog4/Ftr8, Rog4/Ftr2, Rog5/Fr4, Rog7/Ftr5.
Also, if you could explain how exactly you come up with the CR for a goblin. I know adding associated class levels adds +1...