Roger and others never bothered to hone swordsman skills that’s it the same goes for Oden they never really bothered about mastering the blade .
I don't know if you can say that. The argument that they didn't bother hence why they don't have it not only devalues the significance of a black blade but it is also a bit contrived coz we know that they are competent with the sword.
You can make that argument for someone like Linlin who wields a sword like a friggin club lol but not the likes of Roger, Shanks etc.
Moreover, correct me if I'm wrong but I vaguely remember Tenguyama stating that Oden could've potentially also awakened a black blade if he lived long enough to.
So imo there has gotta be a restriction or criteria for Black Blades irrespective of strength that people like Roger, Ray, Shanks didn't fulfill hence why they don't have it. As Roger clearly didn't lack strength.
Made this comment which didn't really get any traction

but it is quite possible that this could be a factor as there are no known Saijo blades that have been made black.
Also I'm just spitballing here but maybe it has something to do with the grade of the sword?
Roger, Issho, Nasujuro all have Saijos so maybe if your sword is already maxed out you can't transform it into a black blade.
iirc when you make a sword a black blade it goes up a level, which implies that Yoru wasn't always a Saijo and that Mihawk only took it up to that level after he turned it black. Coincidentally Shisui is a Owazamono, so wasn't maxed out as well. All of Zoro's swords are also below Saijo. Just food for thought.
*Can't remember if Yoru was stated to have always been a Saijo tho, in which case this hypothesis would be wrong.
In addition to Haki proficiency (be it CoA, CoC or both), I think a user's relationship with the sword is probably going to turn out to be a significant factor with regards to whether a blade can turn black or not.