Hey dave,
I would recommend the Discoid roach(Blaberus discoidales) for your colony. They are a nice sized insect, and are, in my opinion, the fastest reproducers of the non climbers. I have never kept death heads, but being from the same genus, I would believe that their reproductive output would be similar, although I heard that discoids are the fastest. Some other species you might consider are the orange heads(Eublaberus prosticus) and Surinam spotted roaches (Blaptica dubia). They both do really well and are easy to keep and rear. Roaches are very easy to care for; just give them heat, fresh food, and the occasional misting; they'll reward you with many many babies!!. All of these species are also oviviparous, so there is no caring for egg cases, as in some species of roaches.. I hope this helps a little; it's good to see new people getting into roaches, I think that they are going to get reallly popular in the upcoming years, due to their ease of care, large size, and lack of offensive smells which crickets put out... I guess people would just need to get over the "fear" of having roaches in their households.... take care,
bob