50cm road bike for 5'8 height The road bike I'm planning on buying is only available in 49cm and 50cm. Will that be okay given that my height is 5'8/9?
Very unlikely a 50cm (small?) bike will fit you. I'm about the same height and fit a 54/medium in most road bike models.
Some people about the same height with short legs fit a 52cm frame with a long stem fitted.
The manufacturer of the bike you are looking at should have a sizing guide that takes height and inseam measurements into account.
Don't compromise on bike size, get the bike you want that fits you. A frame that is much too small will be a  pain to ride.