Lou, unless you keep your house REALLY WARM, you shouldn't have any issues with any escaped Dubia roaches breeding. First, only fully grown adults can breed, and Dubia roaches (at least the adults) are pretty poor climbers. It's almost as if when they molt that final time they lose a lot of their ability to climb...I'm basing that off of watching several I had in a bin today sorting out a few for feeding. The younger roaches could climb the slick tank while it was inverted fairly well, but the adults looked like they were on wet ice and couldn't climb. So escapees have to molt before becoming adults, and unless your humidity is probably 40% of higher (halfway guessing here), they may not survive the molting process to reach adulthood. And finally back to the temperature thing - Dubia roaches are "Tropical" roaches, meaning they are from Central America and they need warm/tropical temperatures to successfully breed. I've seen numbers all over the place, but the median values I've seen seem to suggest 90-95 degrees for good breeding. If you keep your house between 68 and 72, they won't be able to breed successfully.
The under tank heater I bought was 8"x8" and 8 watts, and it didn't provide crap for heat. I plugged it in straight without a thermostat and after 3 hours using an infrared heat gun the area the UTH was attached was only 88 degrees, so it wasn't going to provide enough heat to do the job. With something covering it, it may have struggled to get to 90 degrees at the bottom. So, I found a foot warmer on Amazon (search for Cozy Products FW Foot Warmer Heated Foot Warming Mat Rubber Design if you're interested) that puts out 90 watts (has a high and low setting), and I put it on my thermostat today. My plastic tank is slightly elevated (maybe 1/2 inch?) on the 4 feet that came with the UTH and it seems to be working well so the contact isn't direct. I need to go double check that the temperature probe is on the bottom of the tank, but when I looked earlier there were plenty of roaches on the bottom and the heat didn't seem to deter them from hiding there with the heat. I plugged a small power strip into the thermostat and plugged a lamp into the power strip while I worked today (I telework full time) and it seemed to be about a 20 minute on/20 minute off/cooldown time (ballpark) with the thermostat set at 93 degrees. Although after seeing Rankins insulation, that may be in the works down the road if I have any more issues maintaining heat. I screwed up with my first tanks because they were too small. I wanted the 12"x12" egg crates standing up so the frass would fall to the bottom and my tank was less than 12" high. I didn't want to reduce the size of the egg crate (trying to maintain as much real estate for them as I can for future growth), so I bought some 27 gallon totes from Home Depot for ~$11 each. The lids hold on well so if they get knocked over somehow the lid should stay put. I figured I'd want a little ventaliation to move air, so I'm letting physics do that for me. I'll cut a 6" hole in the top of the bin on one end, and cut a 6" hole in the tote on the opposite end on the vertical surface. As the heat rises and exists the hole in top, by default it will draw air in through the hole at the other end, slowly circulating the air.