Kevin here - a Shopify Guru :)
It would be entirely upto you whether to check samples of your products before selling them. I know most dropshippers will give you a healthy discount on samples so you can get a better idea of the products you would be selling.
It would of course be an extra cost but it would reduce the risk of returns if you have more knowledge about your product. I would advise maybe getting a small selection of samples from the same supplier just to make sure of the quality of the goods is inline with your standards but as mentioned above, it would be entirely your decision.
Kevin | Shopify Guru