How can I combine similar rows in SAS?

Question

I have data in SAS like this:

Role                      Answer
A                              -
A                         Diabetes
B                             -
B                         Diabetes
B                         Diabetes
B                             -
C                             -
C                             -

As you can see, out of role A, only one answered the question, so the response rate would be 50%. Similarly, in role B two people answered the question. The response rate would be 33.33%. For C, it would be 0%.

How can I combine similar rows so that my data would look like this:

Role                  Response Rate
A                          1(50%)
B                          2 (33%)
C                          0 (0%)

OR

                    A          B                 C
Reponse Rate     1(50%)      2(33%)            0(0%)

I have tried everything I know about SAS.