I've been lucky so far with Foma 400 in 120. Of all their film in roll format, the 400 is the one that gives me the smallest amount of problems. I've noticed no white specks so far, but I haven't used this film for a while - maybe it's an issue that comes and goes across batches.
I don't think stand development, or semi-stand development in Rodinal does Foma film any favours. I'd stick with Foma's official guidelines to start with, they're really reliable - here they are
Foma Product Catalogue
(page 5 for Rodinal/Fomadon R09)
Here's Foma 400 exposed at 250 with an incident meter, in a Rolleicord Va, developed in Foma R09 1:50, continuous gentle inversions first minute, then 1 inversion per minute, 11 minutes in total. Fresh stop bath and fresh fixer. Final wash in distilled water and fotoflo.
Scan is straight out of Vuescan - no grain removal, vignetting, curves, toning applied beyond what Vuescan did. You can see a couple of white specks but that's just dust on the negative.
It's a quite sharp film I found, but it doesn't like being underexposed or overdeveloped. The 400 ISO label is pure marketing and a curse, I think, because its speed is not 400 iso, at least in my own tests (I own and use a densitometer).
I like it for some things but I sadly I don't use it as much as I'd like, because it has a red extended spectral response, which means if I use it to take portraits of white people they'll render looking like corpses (pale face, pale lips).