Q:

Draw only part of a rectangle in Tikz

How can I draw only parts of a rectangle? I want to omit a small part of the rectangle to put some text in. As I'm using various complex rectangles, I do not want to construct own "open rectangles". 
Is there a way to do this? Maybe similarly to using an arc? 

Currently, I'm using 
\begin{tikzpicture}
        \draw[rounded corners=3pt] (-5,-5) rectangle (5,5);
        \node at (0,5) {text with line in the middle from rectangle};
\end{tikzpicture}

I have already tried
to clip the rectangle using an arc or leaving out some part of the rectangle using How can I invert a 'clip' selection within TikZ?, but both got too complex, fragile and did not work. There must be an easy way!?

Update:
Since there are other drawings beneath, using filling color beneath the text is no solution. The following example is a simple one, in other pictures there is even more "lively a background" behind the text...

A:

Your question is not very clear.
Maybe the following code will help you:
\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
  % first solution
  \node (label) at (0,5) {text with line in the middle from rectangle};
  \draw[rounded corners=3pt]
  (label) -| (-5,-5) -| (5,5) -- (label);

  % second solution (with filled rectangle and node)
  \node (label) at (0,4)
  {\phantom{text with line in the middle from rectangle}};
  \draw[rounded corners=3pt,fill=red!10]
  (label) -| (-4,-4) -| (4,4) -- (label);
  \node[draw,fill=lime!10,rounded corners=3pt] (label) at (0,4)
  {text with line in the middle from rectangle};
\end{tikzpicture}
\end{document}

