So there are a plethora of Pho restaurants near Pho 95, no lie. Pho 55, Pho 888, Pho 777 - just add a random number after the word Pho and I'm sure there's a restaurant with the same name nearby. The thing about Pho 95 is that it's packed, every night, while the other restaurants are pretty dead. If that's not indicative of the goodness of the food, I don't know what is.
So Pho 95 has about 8-9 vegan/vegetarian items listed on its menu - and I made an observation, upon overhearing other conversations within the restaurant, there were many vegetarians there too (and that's both times that I went - yes, it's so good that I went two nights in a row).
The Pho Chay is my favorite by far! But be sure to specify vegetable broth. The pho is spicy and chock-full of vegetables, tofu, and noodles. Everything was cooked to perfection; I've never had pho as good as Pho 95's in my life. The vegetarian spring rolls were also very tasty, but honestly, the food comes out so quickly that it's pointless to order an appetizer.
Pho 95 will not disappoint, they were even voted as "Best Vegetarian Meal at a Non-Vegetarian Restaurant in Denver" in 2011 - I will vouch for that. (Be sure to download the PDF version of their menu to see all of the veg options noted on the menu)