Vegetarian cannelloni (and lasagna) is often just a tube of cheese topped with more cheese. Not really diet food! I made a 'meaty' vegan filling and then finish the dish with a tiny bit of cheese. Don't be put off by the number of ingredients. This really is a simple dish. 
For Lentil and Mushroom Filling
Makes 4-5 cups
1 cup dried lentils
2 carrots
1 onion
5 sun dried tomatoes in oil
4 cloves of garlic
2 cups of mushrooms
1/2 tsp Marmite
2 Tbs tomato paste
1 cup of red wine
1/2 cup tomato sauce
hot pepper, salt, pepper, herbs, fennel,bay leaves and Italian herbs
Wash the lentils and cover with an about 2 inches of water. Bring to a boil with a pinch of salt, cover and lower the heat. Cook for 15min until most of the water is gone and the lentils are soft.
Get out your food processor with all its bits and bops. Mince the onion, garlic and sun dried tomatoes. Add to a non stick pan on med heat. Grate the carrots and add to the pan. Slice the mushrooms and add to the pan. Add 1 tsp fennel seeds and 2 bay leaves along with any other herbs and spices. Stir and let all the water cook out of the veg. This will take about 10 min. When the water is almost gone add the Marmite and tomato paste. Mix in. Add the wine. Let the wine cook out. Add the tomato sauce and lentils (drain the lentils first if there is lots of water). Cook for about 10 min, check the taste, turn off and let cool.
Marmite: love it or hate it. But you can't taste it in this dish, it just ups the 'meaty' taste.
For the Cannelloni
1 box cannelloni
1/2 cup tomato sauce
1 ball of fresh mozzarella sliced (125g)
few sliced olives and herbs to top
Lentil and Mushroom filling
Pre heat oven to 200c (400f). Put half the tomato sauce in a big baking dish. Fill the uncooked cannelloni and pack tighly into the baking dish. Cover with the rest of the tomato sauce. Top with the mozzarella, olives and herbs. Cover with foil and back for 20min. Uncover and bake for 10min or until the cheese starts to brown.

Try to let the cannelloni rest before eating, they are hot!!! The lentil and mushroom filling was so rich! I loved it, Saeid said meat would be nicer but he still had 3rds so I guess he liked it!