In a large mixing bowl, add the sweet corn, red onion, jalapeño, Roma tomato, green onion, garlic, and cilantro. Gently stir everything together until well combined.
Add the diced avocado to the bowl and gently fold it in, being careful not to mash it.
Drizzle the lime juice over the mixture and sprinkle with kosher salt. Gently stir once more to distribute the flavor.
Cover the bowl tightly with plastic wrap or transfer the salsa to an airtight container. Refrigerate for at least 15 minutes before serving to let the flavors meld.
Store leftovers in the refrigerator, covered, for up to 5 days. (Note: The avocados may darken slightly, but the salsa will still taste great.)