title: How to change legend description on ggroc function?
body: <p>I'm trying to combine multiple ROC value into one graph, so far I already managed to do that. However, I'm having a hard time changing the legend.</p>
  
  <pre><code>roc.list &lt;- list(roc_obj,roc_objL,roc_objR)
  
  ggroc(roc.list, aes = c("linetype"),legacy.axes = TRUE) + 
                labs(x = "1 - Specificity", y = "Sensitivity") + theme_classic() +geom_abline()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/VfbpY.png" rel="nofollow noreferrer">ROC Curve</a></p>
  
  <p>I can't manage to change the "main" and "1", "2", "3".</p>
  
  <p>I tried adding the </p>
  
  <pre><code>labs(x = "1 - Specificity", y = "Sensitivity", fill = c("Mean Gonial", "Gonial Angle Left","Gonial Angle Right")) + theme_classic() +geom_abline()
  </code></pre>
  
  <p>I expect the output image legend main title to be "Gonial Angle Measurement" and "Mean Gonial Angle", "Gonial Angle Left", "Gonial Angle Right" to 1, 2, and 3 legends, respectively.</p>
  
  <p>Thank you</p>