classifier App - 71.6% accuracy is acceptable?

The classifier app returns me that it is 71.6% accurate. my test data set is 500. i used 15 fold. is it advisable to use my model to classify a data set of 1500 samples. can any one help. what is the use of ROC curve and its value?

[Saravanakumar Chandrasekaran]

My size of test data set is 500