I don't think there's even a reason to think about this much. It's not uncommon for pirate crews to encounter DF and especially not for a crew the caliber of the Red Hair Pirates. Most of all the DF users in the OPverse seem to have obtained a DF by accident. So a crew that travels all the seas has a higher rate of encountering DF than other people.
- The Roger Pirates found the section fruit, which was accidentally eaten by Buggy
- The WB pirates had a rule that whoever finds a DF, can do what he wishes with it (though I think it was stated more specifically that he who finds it, eats it but I assume they have a choice)
- BB joined the WB crew for the specific purpose of finding one DF in particular, which he succeeded in
So for adventurous, powerful pirate crews finding DF isn't that unusual and considering they are already plenty powerful, there's no reason for them to immediately eat it. DF are an expensive commodity, around 100m beri on average. Buggy originally had the intention of selling the DF before he swallowed it by accident. So there's really no reason to think there was some scheme behind this all. Lucky Roo even showed a picture of the fruit to Luffy to figure out if he had eaten it, which indicates they found a DF and later on checked which fruit it was (there's a book of DF). In the same chapter Lucky Roo said that they took it from an enemy.
That Roger had eaten the rubber fruit before Luffy has been suggested before, but you can pretty much ignore it. If that truly had been the case, someone should by now have made a remark about it.
