Seems a little slow
I use all 1500 springs in the rear, 5.1g rollers and my normal flat speed is 45-47mph on the speedo, 30-40 mph uphill.
Sometimes it takes a mile or 2 to all settle in but if you already did a couple miles and its still not right you prob need retune it. Its all trial and error till you find the set up that suits you and your scoot, no 2 scoots are exactly the same.
What type of torque spring is it? Brand name or cheapo? Did you buy the set of 3x different torque springs or just the one?
I had to experiment for ages with rollers and springs till i was happy. Im guessing its a newer A50 you have? Mine is 2008 but a few newer scoots seem to respond differently to older ones, usually 2011-2012 models, dont know why.
If you dont like it as is then leave the rollers but try a 1000 big torque spring. Or if you dont have one of those right now you can refit the stock one and try that, its about 850rpm rated. 20mph is way too slow uphill.
Either way you need heavier rollers or a less stiff spring now to raise the gearing a bit, trial and error, and patience im afraid.