Also can I name this set Substitute+Protect because stallrein isn't particularly descriptive and if I have my way with this it wont even have toxic in its moveset. Subsitute+protect is much more descriptive because thats exactly what Walrien will be doing 90% of the time.
Stallrein is one of those long-standing community-born names that I'd personally like to see stay, I daresay everybody that has ever used this set knows it by that name
good analysis, well done, i don't have any nitpicks for once. I probably wouldn't bother giving Toxic a slash since Roar is absolutely crucial and since this set should really be used with Toxic Spikes support you'll only really be using Toxic on floaty things, the majority of which take fatal damage from Blizzard (Flygon, Zapdos etc) or are immune to Toxic anyway (Bronzong, Crobat etc).
Would maybe mention the use of something that can remove Roserade because she'll just keep removing your T-Spikes if you don't. A decent Pursuit user or Scarf Psyshock Gothorita idk