Drop in from above.

Your legs are short, so you aren't sure if you could catch the cart up from behind, and the back may be closed anyway. You decide it may be safer to climb a tree and drop onto the roof from above.

You scramble up a nearby tree and shimmy across a branch that the cart should pass not too far below. Your slight size and weight is beneficial and you complete the task without too much hassle. You wait, hanging on for dear life, waiting for the cart to pass below you. The rogue continues to grumble about his quest, occasionally stopping to swig from a wineskin. Now he's closer his grumbles sound a little slurred. This could play to your advantage.

You hang from the branch for a second as the roof begins to pass below before letting go and landing on the sloped roof. Unsurprisingly, you begin to slide off, fingers scrabbling at the shingled roof trying to find any form of purchase. Finally, you catch hold of a hatch in the roof, your feet dangling over the moving road below, and you heavy your way up, breathing heavily. You open the hatch and slide in.

Inside there's plenty of goods, mostly bottles, glassware, jars of powders and miscellaneous crates and boxes. It's all lit by a single lantern which has been left on and is to the point of guttering out.

You were hoping for jewels and gold, or at least food or weapons, but you have no idea about most of this stuff. Maybe in a box?

You carefully open a box, the creaking of its lid giving you pause. You look at the slouched back of the rogue, but he seemed more interested in the wineskin than random noises from the back (which were quite considerable with all the glassware). You have trouble making out what is in the box, the light from the lantern is too low. You reach in and feel straw. Rummaging through you find a cylinder with a wick - you must have found a candle.

You decide to light it, hoping the light won't attract attention, because you may as well be blind in here. You open the lantern and hold the wick up to the tiny flame. Rather than a small, steady flame, there is a puff of smoke and sudden hissing sparks coming from the wick!

You panic, waving the hissing, spitting red candle around, hoping it will go out, but instead the sparks travel closer and closer to the candle itself.

"Huh?" Grunted the rogue, turning blearily around, startled by the hissing sound the candle was making.

"Nope, I'm outa here," you think, turning to leave, throwing the candle over your shoulder and bursting through the back door of the cart. You managed around five steps before being picked up and tossed through the air, losing some hitpoints as you skidded across the ground,l.

You ended up in the middle of the road in a small, green heap.