Once you unlock weapon systems, you will have access to the weakest weapons from all three types, but in order to upgrade, you have to further research them separately, as dictated by the usual tech trees.
Also, roles in the game are almost meaningless. Quality/Quantity of ships are all that really matters. However, the game does a decent job of detecting whether you have a support ship or a capital ship. I would simply recommend that you make all ships that are not meant to be on the front lines a Support ship.