Make the chicken and rub- Preheat oven to 425 degrees. Place the baking rack on the lowest setting possible. Make sure to remove the middle and top racks, so only left with the bottom rack.
Remove chicken from packaging. Discard giblets. Rinse and pat dry chicken.
In a small bowl, mix together all ingredients for dry rub.
In a cast iron, pour half can of beer then place can in the middle right side up. Take the dry rub and first pour some in te cavity of the chicken. Carefully, place the opening of the chicken onto the beer can so it is sitting upright. Next, with remaining dry rub season the entire chicken.
Roast chicken for about 1 hour and 15 minutes, until thickest part of thigh, reads 180 degrees.
Remove chicken from the oven once cooked.
Make the potatoes - Make slices in each potato about a quarter inch apart, not going all the way through but close.
On a baking sheet tray, add potatoes and toss with melted butter, trying to get some butter in between the slices of potatoes by pinching them open. Sprinkle with salt.
Roast for 25 to 30 minutes, shaking pan halfway through, until crispy.