Heat 1 tablespoon oil in a skillet over medium-high heat; saute seitan until cooked through and browned, about 5 minutes. Remove skillet from heat and cover with a lid.
Heat 1 1/2 teaspoons vegetable oil in a small saucepan over medium-high heat; saute mushrooms until lightly browned, about 3 minutes. Whisk flour into mushroom mixture using a fork until mushrooms are coated, 2 to 3 minutes.
Slowly pour water into mushroom-flour mixture while constantly stirring with a fork until smooth; add bouillon cubes. Decrease heat to medium-low and continue stirring until bouillon is dissolved and gravy is smooth, 5 to 10 minutes more. Season gravy with cayenne pepper, rosemary, and thyme.
Mix cauliflower into seitan; cook and stir over medium heat until cauliflower is slightly softened, 3 to 5 minutes. Add gravy; bring to a boil, reduce heat, cover skillet, and simmer, stirring occasionally, until seitan is softened, 7 to 10 minutes.