If using canned peas, drain and rinse well to remove as much sodium as possible.
Remove surface moisture by placing peas on clean cloth and rubbing or dabbing gently. Remove any loose skins that may come off during this process. You don't need to rub them off intentionally, just remove those that are loose.
Toss chickpeas with canola oil to ensure a light, even coat.
Spread chickpeas on a large, rimmed baking sheet being sure not to crowd them.
Place in oven and bake for 30 minutes.
Stir chickpeas, continue to bake for 5 to 10 minutes. Keep a close eye on them at this point to ensure they don't burn.
Test doneness, by taking out a chickpea, letting it cool and tasting it. If it's crunchy on the outside but soft in the middle, they need more time. You can also try squishing the chickpea with a fork, if it doesn't crunch - put it back in the oven! They are done when they are crunchy all the way through. But watch carefully, it happens quickly in the last few minutes of baking.
You will likely need to remove chickpeas earlier than others - totally normal. Use a spoon to scoop up the done chickpeas then put the remainder back in the oven. Repeat until all are done.
Place finished chickpeas in a bowl and toss with cajun seasoning or whatever you prefer. Let cool completely before storing.
To store, cool them completely then seal them in an airtight jar. Store for a couple of weeks - if they last that long!
Notes
If your chickpeas have lost their crispness in storage or if they were slightly under-cooked, place them on a cookie sheet and bake them for 5 minutes or so at 400°F.