I have my point of view for them. Their death sound to me, pretty "useful" for the story
Bobby & Teddy :
You can speak few times but you need to go speak with them, like with Teddy before save Saul. But for me, they die, because when Mitch go solo with Basilisk, we can really expect him to die too (like Panam said it). When you see Mitch come back at the end, it's a relief. They die for the "suspense", if I can said that.
Saul :
Without his death, Panam will never become the Aldecaldos "chief". Despite everything they say (and let it appear), there is too much difference between them. For me, I feel like it will never really work between them. And as many quoted, if Panam and Saul go their separate ways, it will be the end of the Aldecaldos. So Saul must die.
Rogue :
If Johnny returns from Mikoshi, he has no real reason to stay in Night City (he really, really lost everything). And if it's V who comes back, well there can only be one boss at AfterLife. So she must also die.
One problem with that... "Fear the reaper" ending... but hey, it's sound quite rare to do it in first playthrough without spoiler.
hence the little sentence: