Do you keep guys like Cliff Politte or Justin Duchscherer on your rosters. They don't pitch many innings and don't offer many K's but can come up with Wins occasionally and Saves if there's an injury. Also both of these RPs have tiny ERAs and WHIPs.
Depends on the league, and my team's particular situation.
You can 'build' one hell of a starter using a few quality MR's. Many of these guys get ignored by managers. A couple in particular (Jesse Crain this year) have just crazy W/IP ratios in addition to low ERA's and WHIP's. W/IP isn't a typical roto category, but if you are on a strict IP limit, these guys can be gold.
H2H leagues some guys target MR's as a strategy. If you draft hitting early or don't have a very deep staff I'd also consider them. When I draft 'well' in smaller leagues I tend to not use them, but there is certainly some value there for the creative manager.
[b][size=18]70*[/size][/b]
* Steroid induced record
I think it depends on league depth etc etc.. but as stated above, setup men/MR typically have little or no value in most leagues. Even in holds leagues alot of quality guys slip through the cracks and can be grabbed for next to nothing.
Scott Shields..... 6 wins, 2.33ERA, 1.33WHIP, 67K, and 7 saves can make a big difference as the season progresses.
I have gordon & taverez (albiet a holds league) but a combined 4 wins, 80K, 2.60 era and 1.15ish whip have been helpers in all catergories.
For the past three years, I've always had at least one stud MR in my lineup (K-Rod, Lidge, Rincon to name a few) just to keep the ERA, WHIP stable and to pick up one to three K's per inning.
This year I'm in a 7-team 5x5 roto league with a SHORT bench but I made room for Pollitte for about a month and got a 0.00 ERA out of him with a couple of wins.
I had to drop him about a week ago to address needs elsewhere but, under normal circumstances, I'll always have a stud MR in my lineup.
As already mentioned, i think it depends on your roster. Some MR guys can help your ERA and WHIP, and vulture the occasional win/save. It'll only hurt you if you try to count on wins out of your bullpen.
Good MR guys are gold in a 5X5 league with anything more than 10 people. Guys who can come in and pitch a scoreless inning with a K or two 3 or 4 times a week really help your ERA and WHIP without eating too much into your innings. They do, however, force you to think more about your SP matchups, because you really need the W from them more than just the innings.
I'm also in a points league that counts holds (5 pts, vs. 10 for win/save), so there are a couple non-closers (e.g. Shields) who rack up decent numbers, but that's about it.