Cook and stir millet in a large saucepan over medium heat until fragrant and toasted, 5 to 8 minutes.

Bring vegetable broth to a boil in a large saucepan; add millet and return to a boil. Reduce heat to medium-low, cover saucepan, and simmer until liquid is absorbed, 18 to 22 minutes.

Heat olive oil in a skillet over medium heat; cook and stir onion and garlic until onion is translucent, 5 to 10 minutes.

Stir onion mixture, spinach, and peas into millet; add wine and rosemary and stir. Increase heat to medium, cover saucepan, and cook, stirring occasionally, for 7 to 10 minutes. Add tomatoes, salt, and pepper; return cover and cook until tomatoes soften, 2 to 3 minutes. Remove saucepan from heat and stir Parmesan cheese into millet mixture.