In a large stock pot (6 - 8 quarts) bring water to boil and salt well.
Chop 1/2 cup of the reserved toasted almonds.
Put the rest of the spinach from the 5 ounce bag in a bowl.
Add pasta to water and stir with large fork or tongs.
Heat pesto on low heat in a large non stick saute pan.
Once pasta is adante (cooked but has a bite to it, not mushy), usually about 4-5 minutes, use a strainer to scoop it out of the pot and add half of it to the pesto.
Add the remaining spinach. Add the rest of the pasta. Add a ladel of the pasta water.
Increase the heat to medium. Toss together in the pesto. The spinach will wilt.
Taste and add cheese if needed.
Put into a large serving bowl or individual serving bowls.
Top with chopped roasted tomatoes, chopped almonds, and grated cheese.