The short answer is yes, a Roth makes perfect sense. Also, if he has, as you say, several IRA's, he might want to consider doing a conversion on one or more of them from the IRA to the Roth,
IF there would be a long term tax advantage to doing so. In order to find this out, he would need to do some calculations to see if there would be any advantage. This website has a calculator that addresses this issue;
http://www.fincalc.com/ (Speaking with his tax/financial advisor about it would be a good idea also) This is a bit off the topic of what you asked but the idea of doing a conversion is attractive for some because it takes a pool of money that will be taxable over time when it is drawn out and converts it to a tax free pool by taxing it all at once. There are some limitations, but when you do a conversion, the entire sum of the conversion is added to the AGI and you pay income taxes on it. It is then (basically) instantly placed in a Roth account where it can be invested, allowed to grow tax deferred and when it is drawn out, is completely tax free.
Reading IRS regulations is a bit like watching grass grow, but from what i gathered by reading the publications i linked below, i am not sure why your friend was told he had contributed too much.
Limit on Elective Deferrals
There is a limit on the amount an employee can defer each year under these plans. This limit applies without regard to community property laws. Your plan must provide that your employees cannot defer more than the limit that applies for a particular year. For 2006, the basic limit on elective deferrals is $15,000. (For 2007, this limit increases to $15,500.) If, in conjunction with other plans, the deferral limit is exceeded, the difference is included in the employee's gross income.
Catch-up contributions. A 401(k) plan can permit participants who are age 50 or over at the end of the calendar year to also make catch-up contributions. The catch-up contribution limit for 2006 and 2007 is $5,000. Elective deferrals are not treated as catch-up contributions for 2006 until they exceed the $15,000 limit, the ADP test limit of section 401(k)(3), or the plan limit (if any). However, the catch-up contribution a participant can make for a year cannot exceed the lesser of the following amounts.
*The catch-up contribution limit.
*The excess of the participant's compensation over the elective deferrals that are not catch-up contributions.
From;
http://www.irs.gov/publications/p560/ch04.html#d0e2474It seems to me that he was within the guidelines of being able to contribute $20,500 because he is older than 50, even if, as you stated, "It appears, however, that not enough lower paid employees contribute". Employees are not required to contribute to a standard 401(K) plan but employers are prohibited from discriminating in favor of higher paid employees. In other words, an employee must be allowed to participate but can not be forced to and if he does, the same contribution and matching provisions would apply to the guy making $40,000 a year as to the guy making $100,000 a year. The company can not have a higher matching percentage for the manager than it does for the loading dock worker UNLESS it is a so called "top-heavy" plan.
How the excess is returned is treated is discussed in this publication;
http://www.irs.gov/publications/p525/ar02.html#d0e2242When the document opens, click on "Retirement Plan Contributions"
If i read it correctly, and from what i understand about these plans, since the $5,000 that was contributed was done so
pre=tax, the five grand would be added to his AGI for the year in which it was returned. At that point he is most certainly free to use it however he sees fit, including opening a Roth IRA. He will have now paid taxes on that money. Also, since he is over 50 years old, he can contribute up to $5,000 in 2007 to a Roth and in '08 the limit will go to $6,000.
Hope that helps.