Rovers led 18-12 at half-time and looked capable of pushing on for a third successive win.
They were also level just before the hour but saw Warrington run riot in the final quarter.
Smith said: “It’s mixed feelings really.
“We competed really well in the first half with one of the big boys in the comp’.
“It was pleasing in some respects but even some of the first half I thought we were a little off our best.
“The second half we inflicted a lot of pain on ourselves, some by the errors but also some sloppiness in our defence.
“You can’t afford to do that against some of the class Warrington has got; they just gobbled it up and turn it into points and they did.
“We’re disappointed overall but I think we’re making progress nevertheless.”
Scrum-half Jordan Abdull and centre Shaun Kenny-Dowall were excellent down KR’s left edge where all their tries came, both scoring one each, winger Ryan Hall adding a brace and Kane Linnett also crossing.
Legendary centre Inglis, 34, scored in the second period on his long-awaited return to the game after retiring two years ago.
The Golden Boot winner also switched to full-back in the second period and came up with a couple of telling plays although, understandably, not resembling the devastating best of his pomp.
Inglis was on Warrington’s left edge initially and it was surprising Rovers did not test him out more earlier.
However, they had plenty of success on the other flank.
Smith added: “I am pleased with the left edge but I’d have liked the right edge to get some more ball as well.
“I think they could have caused some problems over there.
“We just didn’t take the opportunities at the right times.
“Our left side got a lot of opportunities and our right side didn’t.
“It wasn’t just about Greg. I thought he’ll be better for the run but I don’t think he was near his best today.
“I’d have liked to have seen a bit more of a balance in our attack today.
“It was a little too left-side dominant. They are a threat but we have a threatening right side too and we overdid it.”