Beams running through skylight require no alterations to roof structural. This is the least invasive and most cost effective.
Most likely, your existing rafters are spaced 16" - 24" apart.
The rafters can be cut to accommodate the larger skylight opening and structural modifications made to support the roof load. This can be an expensive undertaking.
The rafters can be left intact and the existing roof structure, remain unchanged.
This method also gives a nice aesthetic and can be done economically.