Way too much! Rolen and Glaus were pretty close on draft charts at the beginning of the year. In fact, Rolen may have been higher on a lot of people's depth charts. I know you're probably real sour on Rolen because he's been so awful in May, but he's typically a slow starter. He should turn it around.
Now if you can play Glaus at short (depends on your eligibilty requirements) it's a different story. Glaus is a great 3B, but he's a STELLAR shortstop! Having Rolen and Glaus in your infield would be pretty nice.
See if he'll trade him for Buerhle and some other player. I doubt he would do it straight up, but it's worth a try. Buerhle is definitely a top 20 pitcher, so he's valuable.
Either way, the deal doesn't seem to make much sense, since you're talking about two of the top 5 third basemen. Unless you really feel Rolen will not turn it around this year, and you have really deep pitching, I wouldn't trade Rolen for Glaus if I have to give up one of my top pitchers, too. Maybe a less valuable pitcher and Rolen.
I'm rambling, but I hope this helps. Main point, like you'll see in every trade comment in this forum: It's not wise to sell low and buy high. Glaus is hot right now, so he commands a steep price. Rolen is ice cold, so he won't get you his true worth. It's tough, but the only way this deal is worth it is if you are very confident Rolen will not turn it around.
BTW, if you could pull off a trade where you end up with Rolen and Glaus, maybe trade Rolen to the team that has Nevin? Try for Nevin and another player where you need one. Have Nevin on your bench until he heals. Worth a try!