Flights are available for midweek departures with returns available every day except on Sunday. You'll have the best luck with inventory searching on Tuesday and Wednesday flights, but I was able to see some decent availability on Monday and Thursdays as well.
Searching on the Delta site, I found seats at this price departing CVG on Wednesday, February 27 and returning from LAS on Saturday, March 2, 2019. Other travel days of the week may be available for only $5 more, at $172 roundtrip.
If you don't want to take a gamble on Vegas, we have a huge list of other deals for flights departing Cincinnati (CVG) here.
Need a room in Sin City? Here's what's available from Hotelwatchdog for the sample dates listed.