selecting max timestamp value on a distinct select in mysql

Question

I have data which looks like this:

USER_ID     ROLE            SESSION_ID  TIMESTAMP
f684d34a    VP Marketing    890485E     51:16.2
f684d34a    VP Marketing    890485E     51:13.5
f684d34a    VP Marketing    890485E     51:39.3
f684d34a    VP Marketing    890485E     51:32.2
f684d34a    VP Marketing    890485E     51:20.0
f684d34a    VP, Marketing   890485E     49:52.9
f684d34a    VP Marketing    890485E     51:17.6
f684d34a    VP Marketing    890485E     52:14.2
f684d34a    VP Marketing    890485E     51:41.3
f684d34a    VP Marketing    890485f     51:41.1
f684d34a    VP Marketing    890485f     51:41.4

This is a subset, but for every user_id there could be multiple SESSION_ID and multiple ROLE.

I want to get distinct combinations of user_id and session_id as well as role, but when the role is different when the user_id and session_id is the same, take the oldest role, indicated by timestamp.

Final output:

USER_ID     ROLE            SESSION_ID  TIMESTAMP
f684d34a    VP, Marketing   890485E     49:52.9
f684d34a    VP Marketing    890485f     51:41.1

So as u can see in entry 1, all the instances of user_id and session_id are distinct, but I also wanted role so I took the role of the oldest timestamp for this combination.