A black rough guinea pig is crossed with an albino rough one.

Since we have the least smooth, we can assume that smooth is the recessive trait.  Since black and albino are essentially in a 1:1 ratio, we can assume that albinism is lethal when homozygous, causing death in albino homozygotes (AA's).  (NB: I assume albinism is dominant in this case because lethal alleles are dominant).  This would indicate that the parents are aaRr x AaRr.

If either was homozygous AA, they wouldn't have survived to reproduce.  Rough is the dominant trait, both parents are rough, so they must both carry an R, but they have smooth offspring in the progeny, so they must also both each carry an r.

This is how you get the 1:1 ratio on the black/albino trait and the 3:1 ratio on the rough/smooth trait (all ratios approximate, obviously).