There may be other methods, but here's two that I know of.
After putting your soundpool object on a track, right-click the object. You'll see "Timestretch / Transpose" also "Shift-V". This brings up an interface which has a "pitch" dial. You can change it there.
The second method is to right-click the object in the track and select "Track Instrument Editor". This brings up the VITA control unit. You'll see a "transpose" dial and a "mastertune" dial. You can use these to change the pitch.
I'm guessing the best method depends on the context of what you are doing.
Let me add a third choice - double click the sample and bring up the Master effects rack. You can change the pitch there too with the pitch shift rack. This is useful since you can make EQ settings at the same time.