The website for Metro Tasmania is http://www.metrotas.com.au. When you get onto the bus you should ask for a DayRover bus fare so that you can get one ticket to be used on and off buses throughout the day.
Getting to Rosny Point
Only bus number 670 travels from Hobart city to Rosny Point but this only occurs late in the afternoon. Therefore, from the city centre bus mall in Elizabeth St, Hobart take any bus travelling to the Eastlands Shopping Centre bus mall, Rosny Park. Please be aware not every bus that travels over the Tasman Bridge to the eastern shore of the Derwent River comes through the Eastlands Shopping Centre bus mall, but most of them do. Consider buses numbered 605, 606, 608, 613, 614, 615, 620, 625, 638, 640, 642, 643, 644, 646, 648, 650, 652, 660, or 662. However, I recommend you always ask the driver for confirmation.
From the Eastlands Shopping Centre you have two choices to reach Rosny Point; bus number 670 (Rosny Park to Hobart City) or 675 (Rosny Park to Rosny Park Loop).
Once in the Rosny Point area, get off either at bus stop 20 or 21. Then take the road that travels down to the water from between these two bus stops. Continue walking along the road and eventually it clearly changes to the Clarence Foreshore Trail. This Trail is sometimes marked with a sign naming it. At other times the un-signposted bitumen or concrete pathway, with a broken white line marked down the length, indicates to walkers and cyclists to keep to the left hand side of the path. The Clarence Foreshore Trail continues along the Derwent River in various styles until Geilston Bay, and includes some road walking without the pathway. Along the way it is possible to stop the walk and access various buses.
Leaving from Montagu Bay if you wish
Both the 670 and 675 travel through the suburb of Montagu Bay so, having rounded the Rosny Point and arrived at Montagu Bay, it is possible to catch a bus either back to the Eastlands Shopping Centre, or to Hobart city.
Leaving from Rose Bay if you wish
Once you have left Montagu Bay and walked under the Tasman Bridge, you are in the area of Rose Bay. To access a bus you would need to walk along the Clarence Foreshore Trail for some distance (perhaps 20 minutes) then walk up and away from the Derwent River until you reached the East Derwent Highway which runs somewhat parallel to the River. To bus back to Hobart, you should cross this Highway and wait at a bus stop on that higher side.
Leaving from Lindisfarne if you wish
Continuing onto Lindisfarne and its Bay, four buses regularly pass along the East Derwent Highway. In addition, two buses travel down the main street of Lindisfarne’s village (Lincoln St).
Departing from Geilston Bay
At Geilston Bay there are no buses at the wharf. Two choices: to walk up to Derwent Avenue through the suburban streets south of the Bay and find a bus stop along this road or, as I did, walk for 8 minutes to the East Derwent Highway along De Bomford Lane. Cross the road when you reach the Highway. Wait at bus stop 14 located left from De Bomford Lane on the Highway. If you do not cross the road you will end at the outer Greater Hobart Area suburb of Risdon Vale.