Do I need to mix top soil with garden soil?
I planted a Lilly garden and dug out about if foot of dirt. Most of the native soil was not useable due to the excessive rock. I filled the bed with bagged garden soil and bagged raised bed soil. Should I have also mixed in purchased top soil?
You should be fine. The non-topsoil parts of your mixes will break down over the years so your bed will sink ever so slowly. You can add a 50:50 mix of compost and topsoil (the type I buy has a bit of sand added to topsoil) over the bed to top it off when needed.