Preheat the oven to 200C/400F/gas mark 6. Separate the tops from the carrots and beetroots, wash and put to one side for later. You need to wash the vegetables really well – the carrots and beetroots will need a good scrub, as you’re not going to peel them.
Slice each beetroot into quarters, or halves if they are small, and the carrots in half lengthways, or quarters if they are really big.
Cut the butternut squash in half lengthways and use a spoon to scoop out the seeds (set aside to use later). Slice the squash into 1cm-thick, cresent‑shaped wedges.
Tip all the vegetables into a large baking tray and drizzle with a good glug of the oil from the olive jar. Drizzle about 2 tbsp of the caper brine over the vegetables – this will be your salt – then add the olives and capers and give everything a good mix.
Grate over the zest of the lemon, then cut it in half and add to the tray along with the whole bulb of garlic. Bake for 30-40 minutes, or until the vegetables are cooked through and golden edged.
Meanwhile, wash the squash seeds under cold running water to get rid of any fibrous bits. Coat with a little more oil from the olives, then roast in the oven for 10 minutes, or until you can hear them start to pop and they look a shade darker.
Once the vegetables are cooked, remove the tray from the oven, carefully spoon out the lemon and garlic, and put the vegetables back in the oven to keep warm.
To make the pesto, squeeze the roasted garlic out of its papery skin into the bowl of a food processor. Add the roasted pumpkin seeds, whole roasted lemon and grated cheese, if you’re using it, then blitz to a coarse paste.
Add the carrot and beetroot tops and some olive oil (use up the oil from the olive jar, then add a little more if you need, or just add a splash of water). Pulse until you have a chunky pesto. Season with a little caper brine.
Serve the roast vegetables with the pesto alongside for spooning. Freeze leftover pesto in freezer bag, or keep it in a jar in the fridge, covered with a thin layer of olive oil, where it will keep for up to a week.