The Gentle Roller takes less of your time than hand rolling

Some people believe that the GR takes longer than hand rolling because it typically takes more rolls.   While it may take more ‘rolls’, it’s not true that it takes longer. 
When hand rolling, you are stuck at the table rolling; with a GR you don't stand there watching it go around in circles – you can ride an exercise bike, write a journal, do another lay-up, prepare lunch, tidy the studio or a thousand other things that cannot be done when hand rolling.  If you use the GR rolling time productively (ie on another activity) the rolling time isn’t part of felting time.
All other things being equal (ie the time it takes to prep, lay-up, inspect, hand finish, tidy-up), for hand rolled felt you must add “xxx hand-rolling-minutes". For the GR you can add “zero rolling-minutes" because you didn't actually spend any time rolling.  The GR is therefore less work and quicker. 
Need a more expansive explanation?
Consider baking a particular cake that takes 5 minutes to get the ingredients together, 10 minutes to mix, 35 minutes in the oven and 15 minutes to wash and clean up.
You’re asked how long did it take to make the cake?  You could answer;
(A) 35 minutes – that’s how long it was baking;
(B) 65 minutes (5+10+35+15) – that was the entire duration from start to finish;
(C) 50 minutes (5+10+35) – (don’t count the cleaning time because you cleaned up while it was cooking ie did two things at once; or
(D) 30 minutes (5+10+15) – that was how long YOU were involved in the process – the cooking took care of itself.
I’m going to exclude answer ‘A’ as I don’t think that is what the questioner meant.
So let’s apply this to how long it takes to felt by hand versus the Gentle Roller.  People who say it takes longer on the GR are considering start time to finish time (ie they answered ‘B’ above).  If you count start to finish the Gentle Roller may possibly take longer than hand rolling.  But that is narrow thinking.  It ignores so many other things that may take place in the same time frame.  
If you answered ‘C’ because you did two things at once or ‘D’; because you only count how long you were involved in the process, then you'd also recognize that the Gentle Roller is quicker than hand rolling.
When you hand roll felt, the rolling time must be part of ‘felting time’ – if you roll 1000 times, you are stuck at the table rolling 1000 times!  Start time to finish time makes sense.  With the Gentle Roller, if you roll 1500 times and stand there and watch the machine rolling (a bad habit from hand rolling felt) sure, you might think it takes longer.  But you are not stuck at the table at all. 
As noted above, when the GR is rolling you are free to ride an exercise bike, write a journal, do another lay-up, prepare lunch, tidy the studio or a thousand other things … with the GR, the rolling time isn’t part of ‘felting time’ if you use the rolling time productively (ie on another activity).
All other things being equal (ie the time it takes to prep, lay-up, inspect, hand finish, tidy-up), for hand rolled felt you must add “xxx hand-rolling-minutes". For the GR you can add “zero rolling-minutes" because you didn't actually spend any time rolling, the GR was doing that for you while you did something else. 
And if you make several items at once, or an item with more than one lay-up, the Gentle Roller is even more effective than hand rolling.