I have red a red patch on the roof of my mouth

Mouth lesion: It will be helpful to see it but few possibilities can be - burns ( irritation from food), canker sores, cancerous lesions etc. If it does not resolve or worsens, must get it evaluated by your physician.

Red spots: May be due to burn, trauma, GERD, bacterial/viral/fungal oral infection, general body infection, allergies, neoplasms, and so many other reasons. The term "sores" is very general. Please see your Dentist for evaluation and appropriate treatment, especially if your symptoms are of 2 weeks duration or longer.