Imagine this situation. A man finally achieves what he has been trying to achieve for long. When he gets the news, he is sitting in a restaurant. Elated, he asks the restaurant manager to serve all the customers whatever they want, and he will foot the bill for all. There is an expression to describe this free serving of food. It is something like, 'the house is...' Can anyone please suggest what is exactly that expression?
drinks on me or the drinks are on me wiktionary
Indicates that speaker is going to pay for the drinks [meals] consumed (at a bar, restaurant, etc.)
Similarly he could indicate to management "on me" pointing to the assembled crowd