A solid roller has more stuff going on in the beginning and at the end of the ramp to control valve seating velocities with lash in mind. So basically running a hydraulic lifter on that type of profile can result in a lot more overlap and run really lazy. This may not be true in all cases depending on the lobe profile used.
Hydraulic rollers are definitely way more aggressive off the seat than solid profiles. They get away with this because the of hydraulic shock absorber effect and probably some other reasons I can't think of.

For example,
If you look through the comp lobe master catalog and compare the "Major Intensity" numbers, basically the difference in degrees between rated duration and duration @.050 lift on a solid profile you will see what I mean. Hydraulic profiles typically give there rated duration at .006" lift so you just need to look at the Major intensity rating on the left side of the table and compare that to solid profiles. Some of the lazy solid profiles have major intensity numbers in the 32-36 range. the more aggressive profiles are in the 28-30 range. The super aggressive valve train parts breakage stuff is <28 degrees major intensities. The hydraulic roller profiles normally run below 30 degrees and more typically in the 26 degree range and considered extremely aggressive on a solid profile. This is why you see people going solid on a hydraulic with tight lash because of the fast lift off the ramp.
AG.