This 100%. Some of John Entwistle's best tones were a P bass with Rotosound rounds. And some of them were a Thunderbird, a Gibson bass that only gets a limited amount of love here. Go figure.Rounds on a PB is a highly underrated experience. I’ve used them exclusively for almost 50 years. Funny, in all that time, all those gigs and recoding sessions, not to mention all the musicians I’ve played with, I’ve never once heard anyone suggest that they would like my tone better if I had flats.
Speaking of which - I highly recommend the OP to try out a set of Rotosound 66s. That's THE classic roundwound tone. The RS66LD (45-65-80-105) or RS66LF (45-65-85-105) should be a good starting point.