I have a red spot in the roof of my mouth- is it a bad sign for cancer? its not painful

Lots of reasons: Lots of reasons to have red spot, such as burn, cancer, fungal infection, abrasion, and many other reasons. This is not an "over the computer" diagnostic situation. Put down the computer, pick up the phone, and call your dentist. Let your dentest put all those years of education and experience to work for you. You'll be glad you did.