Heat a large non-stick frying pan over medium heat; cook chicken 4-5 minutes per side or until cooked through. Slice and set aside.
Place stock in a medium bowl; add couscous; stir with a fork, cover and set aside.
Reheat frying pan over high heat; add oil, asparagus, snow peas and capsicum; stir fry for 3 minutes or until just tender; add to couscous with lemon juice and chilli sauce, mixing well.
Serve with rocket, chicken and extra chilli sauce, if desired.