I was that speed with Meyer yesterday... you're faster than me at 4x4, so it probably won't take long to get down to this speed!
To improve with Roux, it's about practising in the right way. Slowing down and looking ahead is even more important with Roux than it is with CFOP; you should only need about 3 TPS to get sub-20. If you try slow turning and maybe get a bit more efficient with blocks, you'll be sub-20 very quickly.