The department may employ an actuary. Such actuary shall, together with such other duties as the secretary may assign, be responsible for:
(1) Advising the secretary on actuarial matters of the state retirement systems.
(2) Making periodic valuations of the retirement systems.
(3) Providing actuarial analyses to the Legislature concerning proposed changes in the retirement systems.
(4) Assisting the secretary in developing a sound and modern retirement system.