Add your chuck roast to the slow cooker with beef broth, ranch seasoning & 1 sliced onion. Cook on low for 6-8 hours or high for 4-6, beef should be easily shredded and tender.
In a large pan, melt 2 tbsp of butter and sauté thinly sliced (2-3) onions over medium heat. This will take about 10 minutes to fully caramelize until an amber color.
Preheat oven to 350F. Slice Hawaiian dinner rolls in half and layer on shredded beef, caramelized onions & slices of Swiss cheese.
Cover with foil and bake for 10 minutes. Brush melted butter onto top of rolls & layer on shredded cheese. Bake at 475F until golden and bubbly.
Dip sliders into excess broth from slow cooker.