Difficult to compare, they are young players with different skill sets who were playing under different managers in a different league.
It could very well be that Rogers is being much better utilised, is maturing more quickly and suits the system better, and Ramsey "peaked" at that level and may not be transposable to the premier league, as happens to many good championship players.
Some decent premier league players also don't seem to get significantly better when they drop down a division, I'm thinking of Westwood and Ayew when we got relegated.
All speculation mind you, I haven't seen anywhere near enough of Ramsey to make that judgement and he may well end up being the better player