The phrase as well as functions like the word ‘and’, and is slightly more formal. However, as well as is not synonymous with ‘and’, and as well as can not always be used instead of ‘and’. The phrase places slightly more emphasis on the items that were listed before it.

Several case studies are presented based on information gathered from the inscriptions as well as from the archaeological material.

Here, the implication is that the inscriptions are the primary source of information. The archaeological material is not exactly lessened in importance, but it is simply not the focus.