ROLLBIT consist 7 letters with 6 of them using white colours so yeah to add more visibility to that, dark background need to be added. On top of that, Southampton's shirt are usually bright in colour so yeah it doesnt really fit that well in term of colours but nah what matters is the visibility. Fans would be able to read it from quite some distance whenever Southampton play
In design and visual effects, you are right but it seems that you are go to extreme here. People will see the logo of Rollbit on Southampton's shirt directly that will be effected by the graphic design but if you see there are other ways for people to see it, you will see that the disadvantage become smaller.
People can see the logo on big screen at stadiums and they can see it on televisions, newspaper too. I don't bring this point to say that the design does not need to improve, next season, not this one when all club's shirt designs for home, home away kits are submitted and approved by FA. It's too late for changes for this season in my opinion.