What is one's duty toward a colleague who does not pray Fajr until after its time has expired, and is it permissible to disturb a sleeping person to awaken them for prayer?

Intentionally delaying a prayer beyond its prescribed time is forbidden and a major sin, due to the warning Allah has issued for those who do so, of a valley in Hell. Therefore, the questioner should advise those who commit this act, for offering advice is obligatory upon a Muslim towards another Muslim, even if the advised person does not seek it. If the advice is not heeded, then there is no blame on the questioner for turning on the light in the room after returning from prayer.