1st rounders can be told to go overseas, but they tend to be international players who are already playing under a professional contract. As twenty four covered, Portland drafted Joel Freeland from England at #30 and last year the 76ers selected Petteri Kopponen (then traded him to Portland) and he's still in Finland playing.
Fran Vasquez was a lottery pick, but chose to stay in Spain. The Magic retain his NBA rights until they waive him or sign him to a contract. I'm led to believe the Vasquez refused to sign the Required Tender which is offered before a Player Contract, along with deciding not to buy out his contract. If Vasquesz had his contract bought out, and signed the Tender then he would of been required to attend Orlando to fulful his contract. Since he refused then the Magic still own his rights.
Remember that the majority of 1st rounders are college players, hence they have no contracts in place with any other team. At the time Vazquez had two years remaining on his contract with Unicaja Malaga and decided against buying out his contract (remember you can only sign 1 contract at a time).
As I said, there really only happens with international players.