By Nina Chestney and Joseph Nasr (Reuters) -Russia said on Monday it will not supply gas to Europe for free as it works out methods for accepting payments for its gas exports in roubles but G7 nations refused the demand. At a meeting of European Union leaders on Friday, no common position emerged on Russia’s demand last week that “unfriendly” countries must pay in roubles, not euros, for its gas in the wake of the United States and European allies teaming up on a series of sanctions aimed at Russia. Concerns over security of supply were enhanced after the demand, with companies and EU nations …