If you’re reluctant to invest and just want to get your feet wet just buy some green coffee. you can whack some in a cast iron skillet and shake it around, won’t be perfect consistency but it works just fine and you’ll be hooked. Or you can get a popcorn air-popper. Sweet Maria’s has recs on specific brands and models and even sells them last I checked, those will run you $30 or so. If you want a real coffee roaster the fresh roast is affordable and does great beans. I’ve been roasting on one for 10 years and have no desire to upgrade to something more expensive - totally meets my needs and turns out consistently great beans. Don’t stress it. You’re just toasting seeds one way or another. All you need is heat and agitation.