Heat tape is by far the superior way to heat your Dubia roach colony. It is much safer and more economical than heat mat/pads, light bulbs or infrared heat emitters. While it does have a slightly higher initial cost, over the long run it will be the cheapest heating solution. This heat tape is 12" wide and 23 watts per foot. Heat tape should not be run without a power limiting device such as a rheostat. You will need to purchase a wire set for each heat tape connection.
Sold by the inch.