Preheat the oven to 220ºC/200ºC fan.
If you have any larger potatoes, chop them so that they are all roughly equal in size.
Place the potatoes in a large baking tray and toss the potatoes in the olive oil (1 tbsp).
Season with salt.
Smash the garlic (a few cloves) - No need to peel the garlic, it just needs to be smashed a little to release the flavour. I simply give them a couple of bashes with a rolling pin.
Scatter the garlic and rosemary over the potatoes.
Place in the oven and cook for 30 minutes until the potatoes are soft and tender - It's a good idea to turn the potatoes halfway through the cooking time to help them cook evenly.
Once cooked, remove from the oven and serve.