Can CAN-Jaguars be used with the roboRio via the RS-232 port on the roboRio?
Yes, but it’s easier to use the built-in roboRIO two-wire CAN terminal.
How would wiring an old jaguar work with the CAN terminal?
See: Wiring CAN Jaguars in the 2015 System
And don’t overlook: Updating CAN Jaguar Firmware
There is a Jaguar bug that new firmware fixes.