I believe the same is not part of the public SDK, you would have to open a partnering case with Nokia to get them.It used to be part of the BAK earlier and one could get it via Symbian platinum partnership program. Also from 5th Edition onwards its not even part of the SDK, i.e. has been deprecated, wonder why that should be.
Did you try the DevASR classes they also seem to support the same thing however there is hardly/no documentation available for the same.
Text to speech seems to be the easier part and people have had some success with it, check wiki for that.
Sensory has a LIB for speech recognition you can check with them, howver thats also not free.