Its completley normal for a new roller to be stiff to turn. Rule of thumb is if you can spin a roller to 'infinity' (IE you spin it and it keeps on going and going) then the roller is shot. But of course like anything use your judgement when changing. If its excessivley hard to turn then thats not good either.
Based on what your saying, i think your balance shaft belt is a little too tight. You should be able to twist the belt with reasonable effort just past 90 degrees with the engine completley cold.
Alternator belt should have aprox. 4mm of deflection at the longest span. Its alot tighter than you think it should be.
Alot of what i am telling you involves the calibrated hand method and is subjective. Again, judgement is everything..
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Congratulations on the belt job though..you just saved yourself about $500 in labor.