Preheat oven to 450F/230C/gas mark 7.

Strip the rosemary needles off the stems. Wash the veggies, and cut into uniformly sized pieces. If you are using mushrooms, wipe them clean with a damp paper or kitchen towel. Mushrooms are like sponges; if you wash them they absorb water and get soggy, not crispy on the outside.

I start with the carrots. The fat ends of the carrots are about an inch wide. The thinner ends might be a little longer.

Then I cut the other vegetables to be the same size. Some very round potatoes get cut lengthwise, long thin ones get cut in half. Small ones stay whole.

Combine lemon juice, oil, garlic, rosemary needles, salt (if using), and pepper in a blender. Puree until smooth. Taste and adjust seasonings.

In a large bowl, toss potatoes, mushrooms, and carrots with the marinade. Season with salt and pepper. If it seems too dry, add a little extra olive oil, making sure all the pieces are completely coated. Place on a rimmed baking sheet or in a large casserole dish that has been sprayed with cooking spray or lightly oiled.

Bake for 20 minutes. Stir the veggies. Cook 10 minutes more. Scatter the tomatoes over the vegetables. Stir again. Cook another 10-20 minutes until golden brown.