You can make ramps easily by using the brush tool. Click on the white cubey icon on the left hand side (the brush tool) and make sure that "block" is selected in the right hand panel. Draw your block, press escape and then select the vertex manipulation tool, the wireframe icon at the bottom on the left hand side. Then select any two top vertices that share a side and drag them down to the bottom. If you drag them right down on top of the bottom vertices it will ask you if you want to merge them. Click ok. That'll give the basic triangular ramp that you can set up next to another square block to make the ramp in your picture. Another way would be to use the clip tool (one above the vertex manipulation tool if I remember correctly) and just cut the ramped side away from your square block.
It's actually very easy if you try, I just have a knack of making things sound far more complicated than they really are...
EDIT: damm I'm always so slow with my posts that by the time I've finished them, 2 or 3 others have already beaten me to it! I second the advice on the not rotating stuff though, I didn't realise this at first and couldn't work out why my beautiful brushwork always ended up so wierd. Rotating by 90,180,270,360 (?!) degrees shouldn't be a problem I don't thing though.