solving a beam and a torsion spring

yuri_elohssa

1. The problem statement, all variables and given/known data
let there be a beam connected to a wall at one end (left).
in the other end there is a cylinder attached to the beam with an inertia moment of I0
the cylinder is then connected to a torsion spring which is connected to a right wall
the beam (cantilever) has a inertia moment - I ,young modulus - E and the length is L.

2. Relevant equations
what are the exact boundary conditions of the problem? (I believe there are 4
2 of the left ones are trivial)

3. The attempt at a solution
I thought of simply saying the torsion moment in one end has to be: tau=k*theta
where tau is the torque and theta the angle of torsion (k is the spring constant), then i can find a connection between the height of the beam and angle of torsion
(although not a linear one)
but there must be another boundary condition...