I believe "conduire" places more focus on the action of driving, and by extension, the driver.
On the other hand, "rouler" places the emphasis elsewhere, and thus applies to driving in a broader, more figurative sense, and thus can include the driver, the passengers, and/or the car itself.
"Je counduis (la voiture) à l'aéroport." - "I am driving to the airport." - I feel this answers the unasked question of "Who is driving?" It's me; I'm the one who is physically driving the vehicle to the airport.
"(Je/On/La voiture) roule à l'aéroport." - "(I/We/The car) drive/s to the airport." - This takes the focus off of the act of driving. We all cannot physically sit in the driver's seat and drive the car; neither can the car itself.
Alos, "conduire" is transitive (takes a direct object) and "rouler" is intransitive (does not take a direct object) when meaning "to drive."
"Je conduit la voiture." - "I am driving the car."
"Je roule en voiture." - "I am driving by car."
There may be exceptions, but I think a good "test" is whether or not changing the verb to "aller" changes the general meaning of the sentence. If it does, then "conduire" is appropriate, if the meaning remains the same, then "rouler" is more appropriate.
According to Larousse 'She rides' is a correct translation. rouler à moto/à bicyclette to ride a motorbike/a bicycle; see: http://www.larousse.fr/dictionnaires/francais-anglais/rouler/69293
I agree that "to ride" is a possible meaning in this exercise. Other possible meanings are "to drive" and "to run". Example:
- Ma mère roule trop vite (= My mother drives too fast)
- Je roule/Nous roulons à l'aéroport (= I drive/We drive to the airport)
- Ma mère roule en mini-bus (= My mother rides in a mini-bus)
- Cette voiture roule (= This car runs)
"rouler" also has some meanings which are unrelated to transportation: to roll (intransitive and transitive), to wrap something and to fool somebody (colloquial).
I would appreciate a full explanation of this verb, if anyone is kind enough to do so. I have read a bit about it elsewhere and on DL comments, and remain confused. I have been marked wrong in this unit for "drives" "runs" and "goes" and have no idea which variation I am supposed to use when. My responses are pretty random at this point.