Roast chicken

I'm suddenly very into roast chicken, but can't figure out the 'trick' behind them. I used to think 200 deg C for 20 mins has been a rather fullproof cooking temp for most things, even for chicken, but somehow it hasn't been working so well recently.

Came across 2 recipes,

Sage & Onion Roast Chicken and Buttermilk Roast Chickenand although recipes call for 220 deg C, and the portion sizes are more or less similar (1 whole chicken or 10 pieces) yet the timing varies greatly. In fact, the 1st recipe is for 10 pieces and takes 1.25 hours, but the 2nd recipe is for 12 pieces yet takes only 1/2 hour.

Well hopefully with more experimentation, I'll get the hang of things. I'm always on the look out for fast and rapid roast chicken recipes cos hey, who's really got the time to sit and wait for a chicken to roast, eh?