Which factor was a major reason Robert Eastman created film rolls?

Robert Eastman (whoever he was?) did not invent roll film. George Eastman developed roll film as he saw this would be the basis of a movie industry.

He bought the patents from the inventor a Peter Houston, whose brother David filed the patents in 1881. This he licensed to George Eastman. The brothers continued to be active in this area of invention, and upon his death in 1912, his collection of patents was sold by his estate to Eastman.