You can use TRolke only for a simple Poisson counting process, where you observe n events and you have Nsig expected events and Nbkg from background.

If you have values obtained from a fit using RooFit, you should use RooStats to compute confidence interval. TRolke uses the profile likelihood method, so you can use in this case the ProfileLikelihood calculator from RooStats (see this tutorial).
Instead if you need to compute an upper limit is better to use the Asymptotic calculator from RooStats.
(see this other tutorial).