Solid 3 star, for clean modern rooms and staff. Great location!
Note: I review hotels on a star-level basis. Read review to get the full idea of the experience.
We stayed three nights from January 26th to 29th 2012. We were there for business at a conference held at the Nationwide Arena.
The Red Roof Inn Columbus Downtown – Convention Center offered a solid 3 star experience at a fairly small establishment, considering the other options available.
It is well located in relation to any possible conference or event, considering that the convention centre is just across the street and that Nationwide Arena is about a 5 – 7 minutes walk up the same street. 
In my opinion, the size (smaller) of the hotel is a positive point. During our stay, there were two more large conferences/events and this usually means poor service and very long wait times for elevators at lunch, supper and in the evening. You would have barely noticed any lines for the elevator, but it did affect breakfast. Granted, they do offer complimentary breakfast, but food selection was very limited (no cereal and mostly pre-packaged) and often ran out. I’m sure the hotel knew of the events in advance and should have prepared better. That said it is included at no extra cost. Another free amenity is the Wi-Fi, but reception was spotty at best. 
The rooms seemed to have been recently renovated in a basic modern style – but very functional. When bunking with others, it’s a plus to have a vanity sink separate from bathroom. Another plus, is that there were always enough towels during our entire stay (we were four in one room). Beds were quite comfortable, but lacked any heft to the bedding. A thicker comforter or a few more blankets would have been perfect, but that may simply be a personal preference. All said, we slept very well.
Staff was really friendly with any questions or concerns. They had directions pre-printed to help us get to some locations and the shuttle ran a tight schedule to help people get to their flights on time (too bad it stopped at 5pm).
I have no problem recommending this hotel if you are looking for a very decent room at a great location near convention centre and arena.
A solid 3 star.