Yes, the machine gunning of the bedroom was done largely for dramatic purpose (just as the machinegunning of Tattaglia and the hooker he was in bed with, by two shooters, in GF was done for the same purpose). Also keep in mind that Roth was not a member of the Mafia--not that it mattered, because...
...as you'll find here, Cristina, the Mafia is mostly made of myths, such as "the Mafia doesn't deal drugs," and "the Mafia doesn't kill civilians." BS! They'll sell their grandmothers' kidneys if they can. And they'll kill anyone and anybody who gets in their way, or to get their own way. As Enzo wisely points out, not even the so-called "traditional" Sicilian Mafia abides by this mythical "rule."