Add 1/8 inch of oil to a skillet over medium-high heat. Shallow-fry potatoes and cauliflower separately until light brown, 5 to 7 minutes each. Transfer to a bowl.
Add 1 tablespoon oil to the same skillet and reduce heat to medium. Add roasted cumin to the hot oil; saute for 1 minute. Add garlic and green chile pepper; saute for 1 minute. Add onion and ginger garlic paste; cook and stir until onion is translucent, about 5 minutes.
Add tomato and season with salt. Cook until tomato is soft, about 5 minutes. Add chile powder, garam masala, turmeric, cumin, and coriander. Taste and if mixture is a little sour, add sugar. Cook for about 1 minute. Reduce heat to low, add water, and cook until garam masala is cooked well.
Add reserved potatoes and cauliflower. Mix well and taste, adding lemon juice if needed. Add fenugreek and cook, covered, for about 1 minute.