Roasting Roots and Creeping St. Johnswort

I was wondering what the best method for roasting roots was, should I dry them first, open flame, oven?

Are you thinking of roots such as dandelion and chicory? These and many others can be roasted in an oven. The roots must be dried first, and broken into smaller pieces before roasting. There is an excellent set of directions on how to do with dandelions, but these same directions can be adapted for other roots:
www.prodigalgardens.info/dandelion%20coffee.htm

Also I purchased a creeping St. Johnswort and have no idea how to care for it. I guess I'm asking what is the difference between a creeping plant and a regular plant (medicinally, I know what the term "creeping" means).

St. John's Wort is a species of Hypericum. There are many known species of Hypericum, so you have to be sure of the species you have. That said, it is a known feature of the medicinal species, Hypericum perforatum, that it can be low growing in the first year and then grow upright in the second year when it flowers.
The true St. John's Wort needs full sun and good drainage. It doesn't require much more care than to provide those conditions. Fertilizer will give you bigger yields but I have heard that there are studies that show that fertilizer doesn't increase the medicinal properties, and that it is actually better not to fertilize.