Just to clarify, you actually have just a “Rocker” suspension, not a “Rocker-Bogie”. A rocker joint is one that has a differential. Move one side of the rocker and the other side moves the opposite amount. A bogie is a passive pivot.

The Mars rovers (pathfinder, MER, and now MSL) have the same design of a rocker to start with but then adds a bogie in the back. The front leg of the rocker has one wheel and the back leg of the rocker has a bogie attached with two wheels, free to pivot front to back. That’s how you get the six wheels compared to your 4. Only 4 of the 6 wheels will rotate for steering (the two rocker wheels and the back two bogie wheels). There is a fundamental difference between driving forward and backward with this design. If a rock flips the bogie it can get stuck in something called bogie-lock.

If a full rocker-bogie is too complicated, but you want more wheels for more traction, you should look at pictures of the European ExoMars rover. It uses a bogie-bogie-bogie setup with six wheels. The back-left and back-right wheels are each on a bogie pivoting front to back (like your rover but without the differential bar) and then a third bogie for the front two wheels pivoting left-right.

Very cool. I like it :)

the rocker bogie suspension is pretty cool

This is what meals-on-wheels suppose to look like.

Omniwheels / mechanum wheels (as suggested in the blurb) wouldn’t be any good for vehicles planning to traverse uneven terrain. They only really work on smooth flat surfaces like concrete or linoleum etc.
Plus they would clog up with dirt too easily.

If they did work then NASA would be using them on their Mars rovers.