I hang my Epson Hot Press Bright roll prints to dry for 24 hours, give or take, and find the the curl usually comes out during that time unless it's near the end of the roll which has more curl. As for the D-Roller, did you buy the 2" or 3" version? I have the 3" version and usually find that a quick roll/unroll and this paper typically flattens out pretty good. The 2" version is typically used for tougher papers to uncurl such as those printed on semiglossy/luster photo paper and I'm sure would more easily produce the reverse curl you describe.
Regards,
Jim