Preheat the oven to 400 degrees F (200 degrees C).
Place chicken, breast side down, in a roasting pan; squeeze juice from 1 ½ lemons over chicken.
Combine sea salt and black pepper in a small bowl; rub all over chicken.
Roll 2 lemons on a cutting board to soften a bit; pierce several times with a fork then place into chicken cavity.
Place the roasting pan in the preheated oven and reduce the oven temperature to 350 degrees F (175 degrees C); bake for 20 minutes.
Flip chicken using wooden spoons or tongs; continue baking until chicken is no longer pink at the bone and the juices run clear, about 1 hour and 15 minutes.
An instant read thermometer inserted into the thickest part of the thigh, near but not touching the bone, should read at least 165 degrees F (74 degrees C).
Rest chicken before serving for 10 minutes. Cut remaining 1 lemon into slices. Transfer chicken to a serving dish; garnish with lemon slices and rosemary sprigs. Pour juices from the roasting pan over chicken to make it super juicy.
Lemon-Roasted Chicken with Rosemary · Dinner Match Lab | Dinner Match Lab