Easiest/most economical way to build a pickup roller

[jlian]

We were thinking about using a hex shaft with wheels. However, we're not too sure what the best way is to secure the wheels on the shaft (hex shaft collars + hex hubs seem a bit too involved/expensive)

I was looking at Team O-RYAN's Ri3D video and the wheels seem to be secured without much setup.

We are a rookie team so we don't have a lot of resources.. Nor do we have scrap material from previous years. Anything we want to build we would have to order.

Is there an easy way to build this pickup?