Update:
We seemed to have solved our issue, so I thought I’d respond in case someone else needs this info down the line.
To give our rollers some traction with the trucks (so that they’d roll together instead of just the trucks rolling and not the rollers), we did a trick we found on Briar: We took a piece of sewing thread and looped it around the roller core. Then we slid the trucks on over the thread, leaving a bit of thread on either end so that we could see it and make sure it was still there. Worked like a charm! The rollers immediately began to roll with the trucks over the rails. The post on Briar said to use string, but our trucks didn’t have that much space, so sewing thread was what fit for us.
We still haven’t fixed the sliding that we have from left to right, but I’ve read that this can be solved with some washers. Right now it’s not negatively affecting our printing.
Hope this helps someone in the future,
Ashley