Never cooked a baked dinner - any tips/advice before I have a go?

My 8 y/o daughter asked me a few days ago about the idea.

I've never made one myself. My late mum used to be a champion at making them but she's been passed away for 6 yrs.

My oven is a 20-ish yr old electric fan-forced job.

I'm thinking of roast beef or lamb to have a go with. With roast potatoes, carrots, pumpkin, etc.