Clio’s explanation is indeed absolutely correct and the details she gives about the expressions and other situations where the old dative is used are to be learned by heart.
Though it is true that local Greeks may say το ρουλεμάν ροδών, it is grammatically incorrect, as well as technically incorrect. Το ρουλεμάν ροδού is completely incorrect since the noun is η ρόδα which genitive is της ρόδας and not του ροδού!
Grammatically and technically correct would be: το ρουλεμάν τροχού or τα ρουλεμάν τροχού and that’s how you will find it, typing it on google.gr. Alternatively you will find some results for το ρουλεμάν ρόδας but none for ροδών
Το ρουλεμάν ροδών means “the ball bearing of the wheels” which is illogical in this specific context and more so, considering that wheels have two ball bearings. Saying τα ρουλεμάν ροδών would be grammatically correct, but not technically.
The correct use of the word ρόδα is limited to some wheels like underneath a piece of furniture, … mechanical devices such as wheelchairs κάθισμα με ρόδες and a steering wheel on a boat (replacing the tiller) η ρόδα του τιμονιού.
Ο τροχός is more specifically used for vehicles, 2-, 3- and x-wheelers and for other wheel-like items. This specificity is well documented through the fact that composed words meaning “street police”, “caravan”, “wheeled vehicles”, “roller skates” are based on the word τροχός: ο/η τροχονόμος (ο τροχαίος, η τροχαία), το τροχόσπιτο, το τροχοφόρο, το τροχοπέδιλο.
Clio’s advice for a very good grammar is judicious. There will be a new edition in august 2011. It’s for advanced learners though as is the equally excellent grammar of Triantafillidis, Μικρή ελληνική γραμματική in English (2004) (15€) (http://ins.web.auth.gr/ekdoseis/ekpaide ... frasi.html
The overall best grammar is the one written by Χρήστος Κλαίρης and Γιώργος Μπαμπινιώτης, Γραμματική της νέας Ελληνικής (ISBN 9604420259), but it’s in Greek.
To use those one has to have a thorough knowledge of the language and of grammar in general. I always advice my students to build their own grammar based on the grammar and the tables given during the lessons, so that they can build them up gradually, which is less horrifying...