What kind of webcams? Most basic webcams do not require ffmpeg. And SDP files are an one option in some cases but not necessarily. You can any RTMP encoder to send a live stream to Wowza from a basic webcam. This is the basic RTMP live streaming tutorial:
The exception is IP cameras that do not have built-in h.264 support. In that case you do need something (VLC, FFMPPEG, xuggle) in the middle. But I would avoid that, there are so many easy and affordable options. There are also some pricey options, but most of them are easy and well supported.