Those are roll crimps. Generally, the seating die will also have a roll crimp built in. Adjust the crimp by seating the die deeper, adjust seating depth by adjusting the top of the die.
Usually, my process is to first put empty brass in the plate, then put it to full ram. Screw the seating die in until there is tension, but not too much. This is generally where the brass is touching the crimping ridge. Lock the die in place. Seat your bullet in the casing, then press it in, adjusting the seating die until your COAL is where you want it.
Once the bullet is seated to the desired COAL, usually where the top of the brass is at a crimping grove or a cannelure (generally for jacketed bullets), back off the seating stem, then adjust the die down a half turn. You need to remember to back out the seating stem otherwise you will push the bullet in further. Press the bullet back in the die and check the crimp. If you need more, adjust the die down another half turn (or quarter turn) until you achieve your desired amount of crimp.
Lock the die in place, then adjust the seating stem until it touches the top of the bullet. Your die is now set to seat and crimp all subsequent rounds the same way. Generally, it is worth double checking the COAL on the next round to make sure the adjustments kept the measurements. You can adjust the seating stem as necessary, but for the most part, you're good to keep loading additional rounds.
To save on the effort, if you are loading more rounds later after disassembling your setup (or loading different bullets), insert an assembled round you wish to replicate into the shell holder, push the ram fully up, then screw the die in until you feel tension. This tension will be on the crimp, so your next rounds should have the same crimp. Then adjust the seating stem to the top of the bullet. You should be good to go.
