I've seen lots of recipes for this on this website. This is just the way my Aunt taught me to make it with a few changes here and there made by my mother-in-law, whom I dearly loved. This is the first dish I made for the family after I started dating my husband.
Bone chicken. Bring reserved broth to a boil. Cook spaghetti in the broth. When done pour enough broth out to leave just enough in the spaghetti to slightly cover, if you like it cheesier pour out more of the broth and save it until you add the cheese mixture to the spaghetti and use the broth to thin to your preference.
In large skillet melt butter. Saute garlic, onion, bell pepper and sliced mushrooms. After mushrooms are cooked add salt, pepper and chili powder. When all vegetables are soft add cubed Velveeta to them and let melt.
Add Ro-tel and tomato sauce to spaghetti. Stir in vegetable mixture and mix well. Pour into greased 13 x 9 pan and cover with grated cheddar cheese. Put in 350 degree oven and cook until bubbly and cheese is melted. Actually, you will probably have more than enough for the 13 x 9 pan and will have left overs for a smaller casserole, or you can split evenly between two 13 x 9 pans.