Suppose both parents can roll their tongue's but their son cannot. draw a pedigree showing this trait, and label each symbol with the appropriate genotype

We will assume that the dominant allele for tongue rolling is T while the recessive allele is t

If both parents are able to roll their tongue, it means that both must have the dominant allele. If their son is unable to roll his tongue means he is homozygous recessive. This also means that both parents have a recessive allele too hence are heterozygous. The following pedigree illustrates this;  

tttccgugdfhhsvhsfghc

explanation:

yooptfrhtr