I want to be a great roll caster

[tailingloop]

I've never tried a DT line, but have been told they are much easier to roll-cast. Perhaps folks with experience can chime in on this?

If you look at the taper profiles for fly lines from the manufacturers you will find that in most cases, if a line comes in both a WF and DT version, the tapers will be about the same until you get into the back taper of the WF line. This will typically be somewhere between 32 and 38 ft. So they will generally cast the same out to that distance. Beyond that you may find a DT easier to roll cast due to the thicker mid section.