The energetic characteristics of two-shell carbon nanoparticles (onions) with different shapes of second shell are calculated. The barriers of relative rotation of shells are found to be surprisingly small; therefore, free relative rotation of shells can take place at room temperature. The intershell orientational melting of the nanoparticle is studied by molecular dynamics. The parameters of the Arrhenius formula for jumprotational intershell diffusion are calculated. The rotation of shells can be observed beginning from a temperature of 70 K.