How to identify sentiment of a given word from a sentence Use case is like this:

Suppose I have a sentence(review data): The staffs were very kind and helpful. The room is ok for its price. There did not seem to be a heater in the room. So, a bit for our January trip.

Now if I want to know the sentiment of a word for example room then how should I proceed.

I have designed sentiment analysis for a given sentence using bag of words model, but determining the sentiment for the given word from the sentence (review data) is kind of new to me. What approach should I take here ?

Providing some approach or any link is enough.
One of the ways to do it is to build bag of words and apply a linear model for sentimental analysis. Then you can look at model's coefficients - positive coefficient means word is positive, negative coefficient - negative word.