A ridge beam would usually only work if it was new-build, and the rafters were of a suitable size such that deflection was not significant.
If it is an older property, it's likely the rafters will be quite small - say 3x2 or 4x2. In this case, we usually add plywood strips around 200 wide connecting the feet of the rafters to the new floor joists (assuming they are reasonably in line). The lower the angle of the gussets, the better.