Herbed Lentil Patties with Carrot-Parsnip Mash & Roasted Brussels Sprouts

1.5 cups cooked green or brown lentils 

1/2 cup oats 

1/4 cup finely chopped onion 

1 garlic clove, minced 

1 tbsp chopped fresh parsley 

1 tsp dried thyme 

Salt and pepper 

2 tbsp olive or avocado oil (for frying) 

4 large carrots, peeled and chopped 

2 parsnips, peeled and chopped 

1 medium sweet potato, peeled and chopped 

1 tbsp olive oil 

Salt and pepper 

3 cups Brussels sprouts, halved 

2 tbsp olive oil 

1 tbsp apple cider vinegar 

2 tsp maple syrup 

Salt and pepper