Although it is unclear which trait is recessive, i will assume that the alleles for wrinkle are recessive.
R - Round
r - Wrinkle
The round seed is a purebred which means it is homozygous as well so it will be RR.
The Wrinkled seed is homozygous recessive which means it is fully recessive, meaning its alleles are rr.
None of the children will homozygous, they will all be heterozygous Rr
