single word requests - Name for people who cannot pronounce one particular sound

Is there a word in English for the inability to utter a specific sound like the rolled R for instance? In my language, there is a name for people who can only pronounce the uvular/guttural R instead of the rolled R. I'm curious to know if there is a word in English for this condition.

Answer

There is the term Rhotacism

http://www.thefreedictionary.com/rhotacism

which relates to the difficulty in producing what many would consider to be a 'typical' /r/.