Answer:
50%
Step-by-step explanation:
Roan color is controlled by two codominant alleles. Let us assume that the red color allele is R and the white color allele is W. Thus, the roan color would be RW.
Roan color cow is crossed with a white bull;
RW x WW
RW RW WW WW
RW = roan = 50%
WW = white = 50%
1/2 or 50% of the offspring would be roan color while the remaining 1/2 or 50% would be white in color.