A large wheel on a very radical lobe (concave opening flank) requires a larger base circle, or the wheel will partially bridge the depression.
A larger wheel used on a cam designed for a .750" will not have the same effect as a higher rocker ratio (linear), but instead have accel and vel changes throughout the lobe's duration, extending the duration at both ends (very slightly) and varying along both flanks but zero at full lift.
To understand what's happening: a flat tappet always follows the highest point on the cam lobe regardless of its rotation. A roller always follows the closest adjacent point of the lobe (tangency), and this will vary with the roller diameter. The difference can be plotted, but the programs TIKO are proprietary.