Divide.
1/3 / 5
Or multiply by the reciprocal of 5:
1/3 * 1/5 = 1/15
Therefore 1/15 cup of flour is used to make 1 dinner roll.
We can set up a proportion:
5/1/3 = x/5 2/3
Multiply 5 2/3 to both sides:
28 1/3 / 1/3 = x
85 = x
So 85 rolls can be made with 5 2/3 cups of flour.