As far as I am aware, both have a backhaul, but the difference is that the pro’s have an additional WiFi channel at 5.2Ghz. Do note that I have not tested either option but I don’t believe this additional channel does anything specific for Roon, the Eero documentation states that the Pro line is “twice as fast” which I assume is referring to the throughput speeds on WiFi.
If you’re not at a location too far from the router, the hardware version you use may not be too critical, though I would certainly still purchase these units from a place with easy returns, in case one option doesn’t end up working right for you.
I have also located the following threads regarding Eero if you wish to review them: