It's a little bit sad to see Roxy try to so hard to hit on Rudeus, yet forget about Rudeus noticing it, he hasn't even told Roxy he's already married and expecting his first child to be born soon enough. Even if polygamy is normal in that world, aside from the religion Zenith and Cliff belong to, it would still be something he would need to mention, considering Roxy's feelings. She would need to decide whether she accepts it or not. I reckon Rudeus himself wouldn't hesitate for a moment (assuming it wouldn't insult Sylphie), but it's not his call, as nothing will change the fact he's already married.
Regardless, I enjoyed every scene of those two interacting. I doubt Roxy really understands just how much she means to Rudeus. Perhaps it's a good thing she doesn't, considering Rudy's panties religion.