First of all, let's talk for a moment about expectation management.
As a newcomer, one might expect that you can start with any material and will create an amazing end product ... abandon that thought right now!
The most important thing to understand about rosin, is that NOT every strain is suitable for it!
It is estimated that <10% of cannabis strains make good candidates for solventless extraction.
You MUST begin with the highest quality cannabis, and strain selection can be equally as important as the quality and RH (Relative Humidity) of your starting material.
Trichomes are tiny cannabinoid and terpene factories found on the cannabis plant, and it's where the psychoactive and therapeutic properties are developed.
As a cannabis plant matures, the trichomes will change in appearance, going from clear, to milky, to an amber color. Cultivators use trichome opaqueness as an indicator of the plant's maturity and decide when it is ripe to harvest.
So, what does oxidation mean for rosin?
Trichomes never stop oxidizing. Heat, light, humidity, and air are all enemies of cannabis.
If you press older flower, you could expect that your rosin will also turn out dark, due to the oxidation of trichomes.
Have you ever seen rosin that was a really pale, almost white color?
That cultivator likely harvested their plants early when the trichomes were still transparent and didn't wait for full maturity.
Flower should be between 55% - 65% RH.
Flower: Press between 180° - 220° for 60 - 180 seconds.
Hash: Press between 150° - 190° for 90 - 300 seconds.