usetikzlibrary{arrows,positioning,shapes.geometric}

begin{tikzpicture}[%
  ->,
  thick, shorten >=1pt,
  >=latex,
  node distance=7mm,
  noname/.style={%
    rectangle, rounded corners=9pt,
    text width=11em,
    text centered,
    minimum height=3em,
    draw=black!50,fill=black!20
  }
]

node[noname] (configload) {Loads config};
node[noname] (varsdec) [right=of configload] {New variables};

path (configload) edge node {} (varsdec);

end{tikzpicture}

documentclass{article}
usepackage{tikz}
usetikzlibrary{arrows,positioning,shapes.geometric}

begin{document}

begin{tikzpicture}[%
  ->,
  thick, shorten >=1pt,
  >=latex,
  node distance=7mm,
  noname/.style={%
    rectangle, rounded corners=9pt,
    text height=1.5ex,
    text depth=.25ex,
    text width=11em,
    text centered,
    minimum height=3em,
    draw=black!50,fill=black!20
  }
]

node[noname] (configload) {Loads config};
node[noname] (varsdec) [right=of configload] {New variables};

path (configload) edge node {} (varsdec);

end{tikzpicture}

end{document}

draw[help lines,red,<->] let p1 = (configload.base), p2 = (varsdec.base) in (-1.5,y1) -- (6.5,y1)
(-1.5,y2) -- (6.5,y2);

documentclass[11pt]{article}
usepackage{tikz}
usetikzlibrary{arrows,calc,positioning,shapes.geometric}

begin{document}
begin{tikzpicture}[%
  ->,
  thick, shorten >=1pt,
  >=latex,
  node distance=7mm,
  noname/.style={%
    rectangle, rounded corners=9pt,
    text width=11em,
    text centered,
    minimum height=3em,
    draw=black!50,fill=black!20
  }
]

node[noname,anchor=mid] (configload) {Loads config};
node[noname,anchor=mid] (varsdec) [right=of configload] {New variables};

draw[help lines,red,<->] ($(configload.base)-(2,0)$)--($(varsdec.base)+(2,0)$);
path (configload) edge node {} (varsdec);

end{tikzpicture}
end{document}

node[noname,anchor=mid] (configload) {Loads config};
node[noname,anchor=mid] (varsdec) [right=of configload] {vphantom{g} New variables};