You can raise the slider in the mixer to bring the timpani forward. Also, give the timp less reverb. Lowering the verb on only the timp will also help bring it forward.

Thank you. Any ideas about how to make timpani pitches above A playback on Garritan?

You can modify the sfz file in ../ Garritan Instruments for Finale > Programs > 003. Percussion > Timpani KS.sfz 

(NB: Not Timpani 1 KS.sfz, which for some reason is the GPO5 file that's ended up unused in the Finale installation.)

Open the file in a decent text editor, and find the first bunch of <region> tags. Go to the last one of this bunch, on line 106, and change hikey=81 to hikey=82.

Do the same in the next group of region tags for Damped hits (line 187). 

You can do a Find and Replace if that's easier, as hikey=81 only appears twice in the whole file.

While you're there, you may want to improve the tuning by adding group_tune=-101 on an empty line somewhere under the <group> tags for Open and Damped hits (say, line 38 and 119). I also like to reduce the relative volume of the Rolls by adding volume=-10 around line 200 (under the last  <master> tag of the file, before <control>).

Obviously, make sure you have a backup copy of the original in case anything goes wrong.