Does the redness from rosacea normally just go away a few days after IPL treatments or does it take a while for it to go away?

In most cases the redness after ill treatment takes a few days to completely clear. I've never seen it clear immediately. 

IPL is a great treatment for rosacea. Generally, it can take up to two weeks for photocoagulation to occur. With each treatment you will notice an improvement in the redness, broken capillaries, and irritation associated with rosacea. An initial series of treatments spaced four to six weeks  is usually needed. From there, regular maintenance IPL sessions can help keep rosacea well controlled. Best of luck to you.

IPL is the best treatment for redness due to rosacea. The results are not visible immediately but after each session the skin gets better and better. In my experience you need at least three treatments for tangible results. Also be aware that there are various IPL machines on the market and IPL requires expertise for the best and safest outcome.