And how does "रस्ता" fit in here? (I grew up in a state where hindi was a second/third language, so didn't really learn it formally, and so don't know the minute differences between the words) On a side note, when I thought of this question, I was reminded of the song "जाने कौनसा रस्ता" by The Aryans ;)
It is an alternate form of 'रास्ता'. It can be used as 'road' (in a way synonymous with sadak) but the more common use is as 'path'/'way' and in talking about directions. It is also used when you are speaking metaphorically (eg: स्वर्ग का रस्ता - road to heaven)
Eg: हमें ताजमहल का रस्ता बताइए (Tell us the directions to the Taj Mahal).
मेरा रास्ता मत रोखो (Don't block my way)
सफलता का रस्ता परिश्रम से होकर जाता है (The path to success goes through hard work)