Let us assume that the diameter of the smaller coin is "d" units and that of the bigger coin is "3d" units.

Now, when the smaller coin rolls around the bigger coin, its circumference is equal to the difference of the circumferences of two coins. The difference in circumference of two coins is (3?d - ?d) = 2?d units.

Therefore, the number of times the smaller coin rolls around the bigger coin is equal to the ratio of the circumference of the bigger coin to the difference in circumference, which is:

3?d / 2?d = 3/2

So, the smaller coin rolls around the bigger coin 3/2 times.

However, as the question asks for a whole number of rolls, we can say that the smaller coin rolls around the bigger coin 3 times.

Therefore, the answer is 3.