That would be Tymkovich meats. They have a pretty good selection of different sausages there. Tim makes most of them in house.
For German sausage, go to Continental Deli in Cherry Creek or Black Forest Deli in Arvada. Continental Sausage (who owns both of those delis) makes most of the authentic German sausages for Colorado restaurants. Their weisswurst (veal/pork brats) are excellent. You can also find them at Costco.
For Italian sausage, Polidori Sausage. You can get most of their stuff at King Soopers, otherwise you can visit them in North Denver.