How to style UITextview to like Rounded Rect text field?

There is no implicit style that you have to choose, it involves writing a bit of code using the QuartzCore framework:

//first, you
#import <QuartzCore/QuartzCore.h>

//.....

//Here I add a UITextView in code, it will work if it's added in IB too
UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(50, 220, 200, 100)];

//To make the border look very close to a UITextField
[textView.layer setBorderColor:[[[UIColor grayColor] colorWithAlphaComponent:0.5] CGColor]];
[textView.layer setBorderWidth:2.0];

//The rounded corner part, where you specify your view's corner radius:
textView.layer.cornerRadius = 5;
textView.clipsToBounds = YES;

It only works on OS 3.0 and above, but I guess now it’s the de facto platform anyway.