In order for a recessive autosomal genotype to be expressed as a phenotype, which percentage of alleles for that trait would most likely be present in an individual?

For a recessive genotype to be expressed as a phenotype, the alleles must be 100% recessive. An individual would be homozygous recessive. 

Example: Individuals with blue/green(light colored) eyes are homozygous recessive, because the color brown is a dominant color and the dominant allele would mask the recessive allele. 

Basalt rock can be rough or maybe smooth