Is it normal not to move the root of the tooth in orthodontic treatment?

Yes it is.  It is all about the connection, the periodontal ligament (“peri” – around, “odont” – tooth). The ligament consists of a group of fibers made of a protein called collagen. These fibers are what anchor and suspend the teeth in the bone. They join to the root surfaces by inserting into a substance appropriately called cementum that is deposited by living cells. On the other side of the ligament, the fibers insert into bone that is very much alive. The total ligament is like a hammock, allowing teeth some movement in their sockets, and through which they are able to respond to the stresses of biting (force).

yes, its not difficult job. orthodontist can easily upright roots to create space for implant through braces.

This is a very common thing that can happen. The roots need to be bodily moved in order to have room for the implant. When you look at teeth, it looks like there's room. An x-ray shows otherwise. Certain directed forces need to be applied to the teeth next to the space in order for the roots to be apart enough for an implant. Once this happens, the roots will be more upright.