I would leave a bit of shoulder exposed--.060" sounds right. That's about the thickness of a quarter. Then I would very lightly crimp with whatever my normal .38 Spl / .357 Magnum die was. And then I would not load it to .357 Magnum pressures because it's a swaged lead bullet and not a hardcast.

Since you're not loading it to .357 Magnum pressures, you'd also be fine seating the shoulder to the depth of the case mouth and then roll crimping over it. My objection to that method is that you'd be asking for the case mouth to shave lead from the shoulder, to gain a crimp you don't need.

For a full-power LSWC load, you want a hardcast lead bullet. That's about 18 Brinell. They're available from Summers Enterprises (which only makes 18 Brinell bullets), and Missouri Bullet (look under .357 Magnum and not .38 Spl).