Anyone running cross tyres on their Roadrat? If so what are you running want to make sure I don’t waste any money!!

What do you want? I.e. what conditions do you want to ride in and what properies do you want from the tyre?
Why is the bike relevant – serious question, is there limited clearance or something?

On my cross bike, I use Mich Muds for racing in the mud. I have a few problems with them clogging though and they have little protection for rocks. Road work would wear them out in hours.
And Schwable Landcruisers for everyday use. More of a touring tyre. Heavy, horrible lack of feel but quite bomb proof and actually a good amount of grip off road.

I’m also interested in offroad tyres for the RR, saw the ones 18bikes used to shod someones (Bontrager, I think) but they’re a bit pricey!

I use racing ralphs on my cx bike, I’m sure they’ll work on your road rat. I got them from zepnat.

I use Michelin cyclocross jet 28C on my rat which are good on and offroad and also quite light. Probably a be a bit narrow for really rocky stuff.