A weee difficulty with 1+ tracks in piano roll view

This is how I can do that in SONAR Home Studio 6:
First select all the tracks you want to see in the PRV by clicking the Pick Tracks button and choosing the tracks while holding down the Ctrl button.
Then in the upper left, click the arrow in the box above Notes/Velocity and deselect 'Show Velocity on Active tracks Only'.
You don't say which version of SONAR you're using, but if of similar vintage to SHS 6, that should work.