Use a Punnett square to calculate the genotype of the male parent?

Assuming that the rough coat is dominant, and the smooth coat is recessive, the offspring must all have 1 r in their genotypes.  The smooth coated guinea pigs have the rr genotype, and the rough coated guinea pigs have the heterozygous genotype, Rr.  Heterozygotes express the rough phenotype.  The Punnett square would look as follows:


FATHER              MOTHER:   r               r

R                                           Rr             Rr


r                                            rr                rr


The father's genotype must be Rr (and his phenotype must be rough coat).

male parent is Rr