Count Assets Barcodes and Group by Rooms
This does Query uses XML string concatenation to get the result in the format you need.

If AssetID or Description can be NULL then you would have to add additional logic

SELECT  '('+reverse(stuff(reverse(( 
        SELECT A.[AssetID] +',' 
        FROM [dbo].[AssetRegister] A
        WHERE A.LocationRoomID = AR.LocationRoomID
        FOR XML PATH(''))), 1, 2,''))+')'
        , 
        '('+reverse(stuff(reverse(( 
        SELECT A.[Description] +',' 
        FROM [dbo].[AssetRegister] A
        WHERE A.LocationRoomID = AR.LocationRoomID
        FOR XML PATH(''))), 1, 2,''))+')'
      ,LR.[RoomNo]
      ,COUNT(*)
FROM [dbo].[AssetRegister] AR
INNER JOIN [dbo].[LocationRoom] LR
on AR.LocationRoomID = LR.LocationRoomID
GROUP BY LR.[RoomNo],AR.LocationRoomID;


Result


DB&lt;>Fiddle

SQLFiddle

Edit:


  Thank you very much is it possible to get all the 19 rows each one
  with their AssetBarcode 01780, Dell Computer, R001, 4


SELECT  AR.AssetID, 
        AR.[Description],
        LR.[RoomNo],
        COUNT(*) OVER(PARTITION BY LR.RoomNo)
FROM [dbo].[AssetRegister] AR
INNER JOIN [dbo].[LocationRoom] LR
on AR.LocationRoomID = LR.LocationRoomID


Result

AssetID Description RoomNo  (No column name)
01780   DELL LAPTOP R0001   4
01781   DELL MONITOR    R0001   4
01782   DELL CPU    R0001   4
01783   DELL KEYBOARD   R0001   4
01784   HP LAPTOP   R0002   4
01785   HP MONITR   R0002   4
01786   HP CPU  R0002   4
01787   HP KEYBOARD R0002   4
01788   APPLE LAPTOP AIR    R0003   8
...*(19 rows)*


DB&lt;>Fiddle