If the die is for a revolver cartridge (.38 spl, .357 Mag, .41Mag, .44 Spl, .44 Mag, etc), it will be a roll crimp.
If the die is for a semi-auto cartridge (9x19, .40 S&W, .45 Auto), it will be a taper crimp.
Even better, DON'T seat and crimp in one step--separate them.
Get a Redding Profile Crimp die for roll crimp and a Lee Taper Crimp Die (not necessarily the FCD) for taper crimps.