Prepare the Parsnips: Wash and optionally peel the parsnips. Cut parsnips down the center, longwise. Then cut each half into 3 to 4 batons. From there, cut away any tough, woody core.
Spread out the parsnips on a large rimmed baking sheet. Set aside.
Melt butter in a skillet set over medium heat. Stir in the garlic and cook for 20 seconds or until fragrant. DO NOT burn the garlic. Remove from heat and stir in the rosemary.
Pour the garlic butter over the parsnips. Season with salt and pepper, and toss to coat.
Spread parsnips out in a single layer and roast for 10 minutes.
Stir the parsnips and continue to roast for 8 to 10 more minutes, or until tender.
Remove from oven. Taste the parsnips for salt and pepper, and adjust accordingly.
Garnish with parsley and pepper flakes. Serve.
Notes
Choose Smaller Parsnips: Large parsnips can have tough cores. Smaller parsnips are more likely to be tender and require less prep.
To Peel or Not to Peel: While many peel their parsnips, if you have small, preferably organic ones, a good scrub is enough. I prefer leaving the peel.
Cutting: Clean and halve the parsnips lengthwise. Cut each half into 3-4 batons, and remove any tough core. Optionally, cut the pieces crosswise to get 3-inch long parsnip 'fries'. Cut the parsnips in uniform thickness so they cook evenly.
Arrange them in a single layer on the baking sheet, ensuring there's a bit of room between each for even heat distribution.
Don't forget to flip them midway during roasting so you get a nice, golden-brown finish on both sides.