Scoop the avocado flesh into a bowl and gently mash it, leaving some chunks. Add red onion, tomatoes, cilantro, lime juice, and salt. Mix lightly to keep the texture creamy but structured.
Place a wrapper on a flat surface with one corner facing you. Spoon filling into the center, fold the bottom corner over it, then fold in the sides. Roll tightly and seal the edge with water.
Heat oil to medium-high until shimmering. Fry egg rolls in batches, turning occasionally, until golden brown on all sides. This usually takes about 2–3 minutes per batch.
Whisk mayonnaise, sweet chili sauce, and lime juice in a small bowl. Taste and adjust the balance if needed. Let the sauce chill slightly before serving.
Allow the egg rolls to rest briefly after frying. This helps the filling set and prevents burns. Serve warm with dipping sauce.