Roots involved in Erb's palsy are
Erb's point is formed by the roots of C5 and C6, anterior and posterior divisions of upper trunk, suprascapular nerve and nerve to subclavius muscle. So the nerve root involved in Erb's palsy is C5 and C6.
Posterior primary rami of C6- C7
Anterior primary rani of C5-C6
Posterior primary rami of C8-T1
Posterior primary rami of C7-C8