UKU

Okay, so I bought UKU and am trying to use it in FL Studios. In the workstation, B4, for example, is assigned a strumming pattern. But in the piano roll, when I choose B4 along with C2 for a strumming pattern in the C chord, all I get is a B and a C strummed once together. How do you assign the piano roll keys for the strumming patterns? Again, they are assigned in the workstation, but not in the piano roll.