Some amino acids contain sulfur, but not all. Each protein source has amino acids in different quantities, so unless the nutritional information has the full amino acid profile for a serving, it’s not possible to know how much sulfur comes from the protein.
After finding out what the amino acid profile is for the ingredient, you’ll have to do math to figure out how that translates into the amount of sulfur in a serving of the ingredient. It might be the case that someone else has already calculated the amount of sulfur in one mole of each amino acid, and that should be enough to figure out.
http://jn.nutrition.org/content/136/6/1636S.long identifies the amino acids that contain sulfur.
On a side note, Rob suffered symptoms of sulfur deficiency even though he was (iirc) getting more than enough protein from a complete protein source. I think most soylents have far more than the reported amount of sulfur, but without doing a lot of investigation and math afterward, the recipes misreport the truth.