Preheat the oven to 400 degrees F (200 degrees C).
Place chicken, breast-side down, into a roasting pan. Squeeze juice from 1 1/2 lemons over chicken.
Mix salt and pepper together in a small bowl and spread mixture all over chicken using your hands.
Roll 2 lemons on the countertop to soften them a bit. Puncture several times with a fork and cram into the cavity of the chicken.
Place roasting pan in the preheated oven and lower temperature to 350 degrees F (175 degrees C).
Bake in the preheated oven for 20 minutes. Pull out chicken and turn over using wooden spoons or tongs. Return to the oven and continue to bake until no longer pink in the center and juices run clear when the thigh is pricked with a fork, about 1 hour and 15 minutes. An instant-read thermometer inserted into the thickest part of the thigh, near the bone, should read 165 degrees F (74 degrees C).
Let chicken rest for 10 minutes before serving. Cut remaining lemon into slices. Transfer chicken to a serving dish and garnish with lemon slices and fresh rosemary. Pour juices from the roasting pan over the chicken to make it super juicy.