You certainly need some means to attach the rafters to the plates in order to resist wind uplift. Depending on prevailing conditions, your local building code may require a metal connector like a Simpson strap for this purpose.

Most older building constructed after the advent of machine made nails would have used them rather than pegs. Preboring of wooden peg holes is rather infeasible because of alignment tolerances. So, my suggestion would be to use large spikes --- That's what Jack does.