Rovibrational calculations in the intramolecular ground vibrational states of the CH3+-Rg dimers, Rg=He and Ne, are carried out on intermolecular ab initio potential energy surfaces (PESs) calculated at the MP2 level of theory using a basis set of aug-cc-pVTZ quality. The internal CH3+ coordinates in the dimer are kept frozen at the optimal monomer coordinates (D-3h symmetry, rigid monomer approximation). The three-dimensional (3D) intermolecular PESs of both dimers feature pronounced global minima at p-bound equilibrium structures: the Rg atom is attached to one side of the 2p(z) orbital of the central C atom along the C-3 symmetry axis (C-3v symmetry). The intermolecular C-He and C-Ne bonds are characterized by separations of R-e=1.93 and 2.21 Angstrom and dissociation energies of D-e=672 and 935 cm(-1), respectively. The PESs of these prototype disk-and-ball dimers reveal substantial angular-radial coupling in the region of the global minimum which leads to significant differences between the equilibrium and vibrationally averaged separations, R-e and R-0. The 3D rovibrational calculations on the rigid monomer PESs yield R-0=2.54 and 2.43 A and D-0=193 and 474 cm(-1) for CH3+-He and CH3+-Ne, respectively. In general, the spectroscopic constants derived for the ground vibrational states of both complexes are in good agreement with recent spectroscopic data obtained by infrared photodissociation spectroscopy.