I wanted to start an game studio, for pen and paper RPGs, and wanted to know how to research that market.
You start your research from a general perspective of the industry, and narrow it down to a micro-market.
First you have to check the industry that you want to enter in. How are other game studios for pen and paper RPGs faring? How much do they earn?
Once you establish that the industry has potential, look into your micro-market. Look at the neighborhood where you plan to set up that studio. Are there enough customers who would come to your studio to give you business? Perhaps you can do a survey among potential customers in that neighborhood.
When you see that the industry is doing well and that you have a potential market — enough to make your business successful — then go for it!