Calculating Raman Intensities from Static Raman Activities
You have two options in that case.


You can try to understand the frequency dependent (or dynamic)  property in the formulation for Raman activity. This property is a bit complex and is known as polarizability. For Raman spectra,  certain invariants of this tensor are involved in the intensity formulation. Be careful with this.


You can then find the formulae for activity first (by refering to the Gaussian manual and cheking referred literature there). After having a formula, then calculate the components required (including polarizability) individually, and finally obtain the dynamic activity.


You can calculate static activity very accurately and scale it using dispersion relations. Dispersion relations are relations which relate a dynamic property to static ones. (I am not sure if Gaussian has dispersion relation calculation.) In some cases you can calculate dispersion coefficients also and use them for scaling. Important is that you need to verify whether static activity can be scaled in such a manner. (I know that polarizability can be scaled but, not near absorption regions.)