He took over on an interim basis when Craig Harrison left for Hartlepool on 26 May after guiding TNS to six consecutive Welsh titles.
Steve Evans, who has been assisting Ruscoe, will also be retained.
Both stepped up from coaching roles and led TNS in Champions League qualifiers against Europa of Gibraltar and Croatian side Rijeka in June and July.
The Saints kick-off their Welsh Premier season away to Bangor City on 11 August.
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At close,  the benchmark FTSE 100 index was down 27.47 points, or 0.4%, at 6,772.
The price of Brent crude slid fell 3.57% to $46.52 a barrel on worries that oil producers would fail to agree limits on output.
Shares in oil giants BP and Royal Dutch Shell were both down by about 2%.
Shares in UK housebuilders were trading higher on the back of stronger-than-expected mortgage lending figures.
Bank of England figures showed 67,518 mortgages were approved in October, a seven-month high.
Barratt Developments shares rose 2.28% while Persimmon climbed 1.95%.
Shares in BT Group saw big moves after telecoms regulator Ofcom ordered it to make its Openreach business legally separate.
BT shares fell 1.4% in early trade, but then recovered to stand about 1.16% higher by close.
Ofcom said BT had failed to voluntarily address competition concerns, adding it would notify the European Commission of its plans to force the legal separation of Openreach, which runs the UK's broadband infrastructure.
The regulator wants Openreach to become a distinct company with its own board, with non-executives and a chairperson not affiliated with BT. However, it has resisted calls to split Openreach off entirely.
"Ofcom isn't really saying anything radically different today in terms of the actual meat of the changes," said Neil Wilson, from ETX Capital.
"What's concerning investors is the detail of the separation, such as the transfer of pension liabilities and budget autonomy - BT's pension black hole has ballooned to top ??10bn and this is a concern for investors."
On the currency markets, the pound rose 0.64% against the dollar to $1.2497, and was 0.67% higher  against the euro at ???1.1774.

GSA established a Phoenix Bursary scheme to help those affected by the blaze which ripped through its iconic Mackintosh building in May last year.
Of the 100 students given grants, 90 are exhibiting at the Reid Building.
The show has paintings, video work, multi-media installations, sculptures, interactive pieces and photography.
It will open to the public on Friday.
An investigation by the Scottish Fire and Rescue Service concluded the fire was caused by flammable gases from a canister of expanding foam.
The report, released in November, said the gases ignited as they came into contact with the hot surface of a projector in Studio 19.
In the aftermath of the blaze, GSA launched a Â£20m fundraising drive to pay for the restoration of the Mackintosh and its contents.
The art school confirmed earlier this year that Glasgow-based Page\Park Architects would lead the restoration project.
Scott Ruscoe has been appointed manager of Welsh Premier champions The New Saints on a permanent basis.
[NEXT_CONCEPT]
Oil companies weighed on the London market as energy shares were hit by a fall in oil prices ahead of the meeting of Opec oil producers on Wednesday.
[NEXT_CONCEPT]
Students who lost work in the Glasgow School of Art (GSA) fire are showing new work made possible through a special programme set up to help them.