This is my favorite pepper for a number of reasons, and I have grown it for years.
I've had decent germination rates using potting soil on a heating pad. They don't germinate well in the peat pots. I've never heard of using saltpeter.
In my experience over the past 10 years or so, it is important to hand pollinate rocoto (aka locoto in Bolivia) - especially early in the season. I use a fine watercolor brush, and just go from flower to flower every few days picking pollen up on the brush and dabbing the stigmas with it.
For some reason it seems like as the season progresses I have to do this less and less. It could be that different pollinators take notice and start taking over or maybe a temperature thing.
Also I highly recommend overwintering your plants if possible. I have kept plants for as long as 3 seasons, but I know they are good for more than 7. They can get very big, but you will want to cut them back by 30% or so to overwinter them inside. If you do this, you will have fruit two months earlier than you would starting new plants.