I had the Rotosound 55 Solo Bass pressurewounds as my main bass string for about 3 years. I switched to them from the Rotosound 66s after those strings made my fingers bleed. I wanted to maintain the brightness that comes from Rotosound strings, but not have the roughness. The 55s are indeed smoother than the 66s, but there are plenty of roundwounds that are smoother than the 55s.
One positive is that the 55s are made of stainless steel like the regular Rotosound 66s. This is a plus for bassists who are allergic to nickel or other common metals used to make strings.
These strings are middle of the road in terms of tone. Because they're halfway between rounds and flats, they're not great at getting either type of tone. They sit in the middle and not in a pleasant way. I switched to D'Addario Nickel Rounds because I wasn't getting enough clank from my basses. Plus, I lowered my tuning to D Standard, so the 55s were too light for that tuning. Just get a set of rounds if you want more clank or a set of flats if you want more smoothness.
My biggest complaint was that I received the wrong gauge on my last package. I ordered the 45-105 gauge set, but my bass tech measured each string and told me that I received 40-100 gauge strings. For $52 (after tax) for a 4 string set, I expect top quality. But Rotosound failed miserably in the quality control department and that was what made me switch to D'Addario Nickel Rounds, which cost me less than half for a similar 4 string set.
In essence, you're getting a subpar product for top dollar with this set, so I can't recommend them. Rotosound needs to do a better job with their quality control and significantly lower the price of this set if they want it to be competitive. Otherwise, they should discontinue it because there are better options that cost much less.
