Every seating die I've ever used, including the 2 or 3 Lee sets I have, allow you to adjust the die down until the mouth of the case meets a machined lip inside the die. Adjust the die a little further and that lip will create either a taper or roll crimp in the case mouth.
Some folks prefer a "factory" crimp, so Lee makes and includes the FCD with some of their die sets. To the best of my knowledge, their seating dies all still have the ability to roll or taper crimp, depending on their design.
