From Roscommon town to Dublin Airport is about 100 miles or 162 kilometres. Depending on where specifically in the county of Roscommon you are going to, the distance would differ, but not by a large amount.
About 41 kilometres or 26 miles.
About 6 miles.
About 8 miles or 12 kilometres.
Stena Line goes from two places in Dublin. Dún Laoghaire, which is a port on south of the city is about 14 miles or 23 kilometres from Dublin Airport. There is also Dublin Port in the city, which is about 8 miles or 13 kilometres from Dublin Airport.
It is about 147 miles or 225 kilometres.
About 160 miles or 250 kilometres.
There is no actual place called the Dublin Exhibition Centre. There are a number of places in Dublin that have exhibitions, most notably the RDS (Royal Dublin Society). Dublin Airport is about 6 miles from the city centre. The RDS is about 2 miles from the city centre, on the opposite side than Dublin Airport. Most of the other places where they have exhibitions are close to the city too. So wherever the place you are referring to is, it is not far from Dublin Airport, within about 12 miles.
Blarney is in Cork, so to drive there from Dublin airport would take at least 3 hours on the motorway and could be more in heavy traffic.
The main airport in Dublin Ireland, is called Dublin Airport.
Ireland does not use postcodes. There are postal districts in Dublin city, but not outside of that, including the country of Dublin, which is where Dublin Airport is. All you will need is the particular person or company you are writing to in the airport and then finish the address with: Dublin Airport, County Dublin, Ireland.
In good traffic it can be done in about 2 hours.
Initially you leave Dublin on the N4/M4, which is the Sligo road. Depending on where in county Roscommon you are going, you have a choice when you get to Kinnegad, in the midlands of Ireland. You can take the Galway Road, which is the M6 if you are heading to the southern half of Roscommon, or continue on the M4 if you are going to the northern part. If you are going to Roscommon town, you could go either way, as it is central in the county, though the M6 to Athlone and then the N61 to Roscommon town would be slightly better.