I have a Rad Rover and love it. Great way to carry it with forks over the tailgate.
Another way would be to get a pair of these:
Fasten to a piece of 3/4" plywood with carriage bolts and put in bed of pickup. This bracket fits in place of the front wheel's axle and clamps in just like the regular "Skewer" that holds wheel in place while riding.
I'm not so sure how firmly in place the front brake disc pads are. Hanging the fork over the pickup tailgate might lead to loss. Don't know for sure as I just carry my Rover in the back seat with front wheel removed. Just fits with zero clearance on each end.