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I would eat them after. You are at your most insulin-sensitive post-workout. If you did an intense workout and have a faily healthy metabolism, nearly all of the starch will go toward replinishment of muscle glycogen that was burned during exercise. Also, a cup of either rice or potatoes isn't a ton of starch, so it's not a big deal. For potatoes, I think it's around 26g of carbs and for rice around 40g.
Don't beat yourself up or consider yourself not Primal for including starch in your diet. Athletes who use their peak performance (sprinters, powerlifters) require glycogen to perform optimally. On the other hand, if you're doing nothing more intense than jogging at a slow pace or something similar, a low carb diet is fine.