There are IC's that will separate composite and component into RGB, that part is simple enough. Very few RGB computer monitors scan anywhere near the 15.7 kHz horizontal of NTSC though, most are close to double that or higher. Displaying NTSC on one of those requires a scan converter, it digitizes two interlaced fields into a frame in a RAM buffer and then converts that back to a single non-interlaced frame at the scan rate supported by the monitor. It's possible to do, but certainly not worth the effort unless you have a very specific need.