My general comments about this hotel are that it is an old hotel that needs to be refurbished urgently. The bathrooms are moldy and the carpets look disgusting. They also need to do something about their housekeeping.

Our experience of the Viminale consisted of the following:
We arrived late in the afternoon from Florence, and after some time waiting, during which we did not know what exactly the problem was, they informed us that they had lost our reservation. After waiting for almost 2 hours for them to figure out what to do, they gave us a room in the basement for the night, with the promise to change us in a different room for the rest of our stay. The room we had to stay in had not been cleaned in ages and it smelled of urine.

The next day they moved us to a different room which was big, but as I mentioned above very run down.

The breakfast was good and the location not bad, but the staff was indifferent. Not a good experience!

We originally booked to stay at the Hotel Edera but when we arrived at 9.30pm they told us they had double booked and moved us to the Viminale. It turned out the Viminale was actually in a better location (more restaurants etc nearby). It was about 10 mins to Termini and the Colosseum.

The room was a good size as it was actually a triple and the bathroom was great. The hotel was clean and breakfast was lovely - the breakfast terrace was a really nice place to eat.

We enjoyed the roof terrace and the reception staff were always friendly and helpful.

The viminale was recommend to me by girlfriend and she was right. Within walking distance of the Colosseum, Termini and metro the hotel is as well inexpensivce as something special.
The staff are very kind and helpful: I forgot my bathing suit there and they sent it to Germany! Our triple bedroom was nice and clean and the bathroom recently installed and very clean. Air condition was excellent at 34°C outside. The roof terrace offers a nice view of the city. The breakfast is ok but could be optimized. We all would come back!

If you don't mind querky and a bit outdated, this hotel is fab. It's inexpensive and within walking distance of the Colosseum.
The staff are absolutely fantasic and were so kind to us. Yes the rooms are interesting and indeed of updating but they are clean. The roof terrace doesn't have much interest in terms of a bar but there is a nice view of the city. The continental breakfast was lovely. Overall, I loved this hotel and it was definitely a cut above the plastic hotels we get over here.