You don't mention the size or type of the chicken you cooked, without further details it sounds like the bird was overcooked. If the size varies from week to week the results will too.
For perfect juicy chicken you could try the following or combination of methods:
- Use a meat thermometer in the thickest part of the flesh on the leg/breast to test the temperature. You want an internal temperature between 165-175F (74-79C) depending on how well done you want it (FDA guidelines). You can go as low as 71C (160F), but some would not consider that safe.
- Size matters. Smaller joints/birds will take less time to cook. To cook by weight, cook for 20 mins per 454g/1lb plus 20 mins extra (again FDA baseline).
- If using a whole bird, spatchcock or butterfly it. This technique will ensure even cooking of both the breast and the legs and is my preferred method for cooking perfect chicken
- Consider using a brine or wrapping the chicken in foil or a roasting bag to retain the juices.
Another possibility is the type, breed and age of chicken, older birds will be tougher.
If it is purely down to method, see this guide for perfect roasted chicken: https://www.seriouseats.com/butterflied-roasted-chicken-with-quick-jus-recipe