How to add duplicate records by basing on the count from another table (SQL)
You could JOIN the tables
eg
select T1.first_name, T1.last_name, T1.role
from table#1 T1
  join table#2 T2
    on T1.first_name = T2.first_name and T1.last_name = T2.last_name
;

-- result
+----------+---------+------+
|FIRST_NAME|LAST_NAME|ROLE  |
+----------+---------+------+
|John      |Smith    |Dev   |
|John      |Smith    |Dev   |
|Jane      |Doe      |Tester|
|Jane      |Doe      |Tester|
|Rock      |Lee      |Dev   |
+----------+---------+------+

DBfiddle here.